Yeah, you're right. Like @enkiv2 said, it's really about control. If the user controls ordering and filtering, any old order is fine. I think the reason plain old reverse-chronological seems notable is because most people who use feeds are using Facebook, Instagram, Twitter, Reddit and/or Snapchat, where the user isn't in control.
Even if these services offered sorting options (most don't, I think), the default is an optimization for time-on-site. Which is to say, when most people's experience of feeds is being manipulated by them, boring old reverse chronological sticks out.
Even if these services offered sorting options (most don't, I think), the default is an optimization for time-on-site. Which is to say, when most people's experience of feeds is being manipulated by them, boring old reverse chronological sticks out.