That hasn't been my experience at all

You've never held the door for a woman who snapped "I can do it myself" (or similar) at you in response? I have, so we're at an anecdotal impass. Maybe it's that you're from a different area, I mean like, I hear in Italy stuff still flies that would get you called out for sexual harassment (rightly so) here, maybe something like that explains the difference.

Not that I expected anything in return (other than a polite "thank you" but that's from everyone lol) either, but they thought I did (I guess, I didn't ask but why else be a jerk for that y'know?

offer of help to try to get his foot in the door and constantly nose around and bother her afterwards which made her very uncomfortable

But here's the thing, unless she can read your mind, she's uncomfortable already just by you being there (according to women, they're constantly scared and suspicious of men's motives). It doesn't matter if you're actually attracted and trying to start a convo in hopes you hit it off (which again is a normal human condition, even if it is currently vilified), nor if you're actually too pushy and "constantly nose around and bother her afterwards," nor if you start a convo sans attraction, nor if you don't talk to them at all (like me,) they are apparently uncomfortable.

Women aren't so judgemental as you're imagining.

In front of you, where they're default scared. Try when they can pseudononymously speak their mind without fear of physical recourse and they're not afraid to say how they really feel, they sing a different tune.

constantly nose around and bother her afterwards which made her very uncomfortable. He then went around behind her back at our workplace talking about how she rejected him when he was only trying to be nice and so on.

Of course that is a problem but that'd be a problem if he was just trying to sell funko pops, being annoying in general is an issue. But you don't have to do it to make them uncomfortable at the prospect that you could.

set things straight with this guy

I mean I'm not gonna argue, communication is always good. They may argue though that men can't take rejection and they can't directly communicate for fear of violence, but I do personally agree it's the best practice.

If not then they can move forward and base their relationship on actual things that matter rather than just him buying her shit all the time.

Well I can guess what your love language is not. I'm a (receiving) physical touch and quality time man myself so I get it, but people have ways they both show and receive love, and finding a compatible partner is not a bad idea. Sounds like his "giving" language is gifts, who knows what his "receiving" is, and who knows either of hers (no clues I noticed anyway), if hers is "receiving gifts" they're in business it sounds like. Just because one isn't important to you however doesn't mean it's less valid to anyone else.