Because as much as I post across Lemmy, I'm not continuously on all day. I usually post a handful of things whenever I think about it (usually the morning), then catch up on comments later throughout the day.
It just seemed like bot behavior to me that someone would make so many posts so fast is all, but I guess "terminally online" is one way to describe a disabled person.
Maybe you can understand how always having a lot of content primed and ready to go and already having a plan of where to post it so that it can be done quickly seems like a "terminally online" thing from my perspective. It seems like an excessive effort to me for a human to post that much content daily with such a time crunch. In order to repost content in the first place, a human user would also have to be active on multiple social media sites, so maybe "internet addict" would be a better descritpion.