No It's only in certain maych ups.
example:
Trunks (fighting) you vs. Vegeta(com)
You use finish buster, He will say finish buster in japanese.
example 2:
SS4 Goku (you) v.s SS4 Vegeta(com) You win, Goku will talk in japanese.
Good bye everyone, it's been fun!
Special thanks to ED_, superman4u, and Cross Stinger
Credit for the Siggy goes to shadow slayer