Will I automatically do a hip hinge when I bend over if I don't bend my neck?

That may work for you. I just tried it, and I can round my lower back while keeping my neck straight, and I can straighten my lower back while bending my neck.

I’m speaking from a dance background here, not a physical therapy/scientific background (so it might be a little different) but we’d distinguish between two different kinds of bending-over—one where we’d round the back, and one where we’d flatten the back.

When you bend over with a flat back, the only point of (apparent) movement (ideally) is at the crease of your hips. If you look at this dancer’s position, you’ll notice that if you turned the photo 90 degrees counter clockwise, and looked at her only from the hips up, you would be able to think she was just standing normally with her arms raised over her head (more or less). You couldn’t do the same in this image. I mean, it’s stylized, but look at the difference in the back alignment.

For another comparison, here’s an image with one person in multiple poses. Notice how the position of her upper body in A is almost identical to her upper body in C. Notice how in B, to bend farther over, she stopped tilting forward at her hips, and started instead to curve out the spine. Keeping the back flat requires more flexibility—as you tip your pelvis, you will feel a stretch in your hamstrings. (This is an important clue in why a hinge is important).

The trick to hinging is that it’s a quite active process. Your core needs to be engaged. Your upper back muscles need to be engaged. Your glutes need to be engaged. Your hamstrings need to be engaged. If you don’t engage all these larger muscle groups so that they can take and distribute the load, you can (and will) still damage your lower back—because its much smaller muscles will be taking all of that weight in a strained position. Although I stressed above how it looks like someone’s simply folding at a hinge point, there’s a lot of musculature involved in the movement.

The key: when you tip the pelvis rather than curving the spine, you’re allowing yourself to recruit your glutes and hamstrings in the movement (for the same reason that you feel a stretch in the hamstrings when you tip your pelvis—that’s where those muscles attach, that’s where they can pull). And recruiting the core and upper back muscles further distributes the weight across the upper body to protect the lower spine.

When you’re hinging for functionality rather than aesthetics, your knees should be slightly bent rather than locked, and you obviously won’t simply bend over to 90 degrees with straight legs—that’s not a position to pick up weight from; I just used that dance movement as a way to show the pelvis position. The farther the flat back is taken, the more difficult it becomes to properly recruit the other muscles needed to take strain off the back.

I think the author is going a bit extreme to be so opposed to the lower spine ever curving at all—I mean, that’s part of the vertebrae’s natural range of motion. The vertebrae aren’t fused together or anything… You just want to make sure you’re not asking the lower back muscles to take too much weight, and you want to make sure you carry yourself with your muscles rather than crunching into your skeleton. I do agree that using small moments like bending over the sink can be a useful way to practice and develop the muscle memory. (But like I said, I’m also coming from a dance perspective, not a scientific one).

Edit to add: I hope I addressed what you were wondering about?

The version linked by the OP is arguably the wrong way to do a hip hinge, I’ve never seen it taught that way before and you wouldn’t want to do that with anything heavy. The author explains it’s a “simple” version, with the legs straight, but I think honestly more back injuries occur from using that motion than a proper hip hinge. There’s some good info there, I’m not saying it’s completely off, but I don’t think a normal hip hinge is too difficult to learn. For example, I can’t imagine getting anything off the ground like that.

The hip hinge is more about dropping your bottom/pelvis back a little bit first, while bending your knees and tightening your core. More like starting to sit than just bending at the waist if that makes sense. The bending at the waist is more just used for balance or for picking something up (why we bend over most often). As @Soubresaut mentions, a proper hinge engages your larger muscles so you can move something safely and as the linked author mentions it takes practice to become second nature. I think practicing it stiff legged may be counter productive, at least initially.

You can keep your neck straight and essentially just bend at the waist to get all the way down, so the neck isn’t really the problem. It’s your lower back that you need to consciously monitor.

I’d advise looking at a couple other hip hinge guides though to get a feeling for options that might feel more natural and serve you better. Even the NPR story that may have prompted the question shows a more natural, legs bent, hinge as an example.

Thanks for the answers.

From @Soubresaut‘s second image, I see that it is possible to keep a straight neck and not do a hip hinge. Fortunately for me, that position would be difficult to get into. Once I keep my neck straight I tend to flex my knees slightly and get into what seems to be the proper position. It would be nice if there was a video of someone very slowly doing a hip hinge.

Here’s a simple hip hinge video how I’ve seen it taught before. There’s also a animated gif in the linked NPR story.

Youtube has dozens of videos on proper form if you want to check out some others.