Does arterial elasticity have anything to do with flexibility?

I’ve never been flexible. Even as a little girl doing a split was nearly impossible.

I was reading something about vitamin D and it talked about it improving arterial elasticity and discussed it related to blood pressure. Other articles talk about D helping with muscle pain (that happened for me) and I am more flexible now than I was 5 years ago and I do feel the D helped with it.

How is arterial elasticity tested?

I have no idea if arterial elasticity and general flexibility are related though, even outside of the D.

What do you know about it?