This is all interesting. I agree that you can't assume anything based on how authors behave on Twitter. In my experience, the people I've found to be both nicest and most supportive and inclusive on Twitter are authors I've met IRL first. After that, authors I've come to know off some other online platform. Authors I've tried to befriend purely on Twitter have been pretty standoffish. I get the feeling sometimes that there's a "I'm a more important author than you and you're beneath me to notice" vibe, but that's probably just me projecting. It's impossible to know, either way.