I figured out how to tell the difference between bots and real players pre lobby screen. Bots will do emotes and you cant mimic them. You can only mimic real players emotes.
How to get bot lobbies in Fortnite in 2023 - Dot Esports
I tried to get a BOT a Fortnite win and then this happened... - YouTube
How To Get Into a Fortnite Bot Lobby (Chapter 3 – Season 2)