Is it necessary to greet someone every single time you see them?

There’s this guy at my college I’m not even friends with; we’re barely acquaintances (we worked on a mutual friend’s film set a year ago, that’s all. We haven’t hung out since). But ever since last semester he’s been going out of his way to talk to me. Last semester a mutual friend stopped by my dorm for a bit, then as he was leaving he said “Oh yeah, “Z” told me to tell you ‘hey’”...but I’d just seen “Z” like, 2 hours prior and he said hey to me then too (let me reiterate, that I’m not friends with this dude. So why bother relaying a message to me through our mutual friend, esp. when it’s only what “Z” himself already said only a few hours before).

Now this semester literally every single time he sees me he says “Hey (insert my name)”. It’s never just “hey” or “hi”, he constantly uses my name and waves at me. I could be all the way down another hall and he’ll call out to me just to tell me “Hey (insert my name)”. My actual friends don’t even do that. If I was friends with this guy, I’d get it but since I’m not I’m finding this strange. Is it really necessary for someone to hi every single time they see you?