Check pret’s disassembly of the games. He has names for each flag. What you’re looking for might be named.
edit - here: https://github.com/pret/pokeyellow/blob/3ce276892c1b97ae893d319125b13fed936d14f2/constants/event_constants.asm
you may have to trigger flags for the win/lose conditions as tho you were playing the game. It might not be a single flag controlling the species/team, but rather the win/lose flags working in unison.