@tychi so the way Mastodon works, if someone follows you and you don't follow them, and nobody else on your server follows them, then your server doesn't store information about what that person posts. So building that kind of timeline would drastically increase the workload of the server and also have privacy implications where people who aren't followed by you are still being "followed" by you. It's related to why you need to follow an account to add it to a list.

@tychi on paper it seems like the kind of thing I would hate but lots of people seem to like it!