Agreed. Over the years I've touched base with folks who helped me out at crucial times and they didn't even remember the incident. Like one time when I was not offered a job after an internship, this senior guy stepped in and made sure they gave me an offer. I thanked him 20 years later for helping me get my start. He just said, "Really? I don't recall that, but glad I could help." So paying it forward is probably the best strategy.
I had some time in a non-tech gatekeeping position and was able to help a bunch of people, who occasionally thank me for it, and I generally don't remember the details at all, and it's nice and all to be thanked, but I was just doing it because it was the right thing to do. On the other hand I'd be absolutely psyched to hear they were doing it for someone else -- that would put a huge smile on my face.
People who have developed a life pattern of helping other people without any expectation of reciprocal help; often don't remember many of the specific acts of kindness they performed.
His response to your thanking him was perfect.
Yeah, I used to have a similar drive as OP where I thought some sort of grand gesture was in order towards various people in my life. And I can't think of a single time it particularly paid off.
It's not like they go "ah yes, just what I deserve!"
If anything, it puts them in a confusing or uncomfortable position.
I get it now. But if you have people to thank, call them and make it short and sweet. But don't do the big gesture.
I think in some cases it's because the type of person who would go above & beyond to help just naturally does this as their normal course of business. It is routine behavior for them, and each act is not memorable.