1. Public timelines had public API access for a good number of releases. This made tools like unmung.com/mastoview possible
2. A preview of the public timeline has been requested since day 1 of Mastodon
3. Giving a local-only preview may be more useful to experienced users, but I feel it would be underselling the federated nature to new users
4. Local-only timelines are slower-moving and have less content - again, underselling the network
@Gargron solution: have it so on a wide enough display, both columns are shown on each side
@boots the real solution is to turn the header of the component into a tab but i am only willing to do so much work in a single PR
