I haven’t had any break out of Pokeballs yet so I’m just curious if it’s a 100% catch Rae if you host
Defeating the Tera Pokémon within the time limit will cause the Pokémon to cease being Terastallized, at which point the player is given the chance to select a Poké Ball from their bag and can catch the Pokémon. This capture cannot fail.
It doesn't matter if you host a raid or not. You'll always capture the mon.