Ah, you’re right - I mixed up user and home timeline.
For user timeline, you’re getting back the profile Tweets for a user (what you see if you visit an account’s homepage). There’s a rate limit per user of 180 calls per 15 min window.
For home timeline, it is more restricted. That timeline is the one that a logged-in user sees, i.e. everyone they are following. That tends to be a lot more busy, so the rate limit is lower (roughly one call every minute) to save on potential load.
If you are operating under user authentication, then each instance of your application (authenticated as a different user) effectively is rate limited separately. So, 10 logged in users could each make 15 calls in 15 minutes (150 calls in total, but only 15 per user, you can’t “share” that across user tokens).
Note that home timelines require user authentication; user timelines can be retrieved without logging in, i.e. under app authentication, but the rate limit is limited differently.