It does play every time you face him. whether you soft reset, or you make him faint and beat the E4 and go face him again.
Also, that cut scene only lasts like, 10 - 15 seconds. sure it'll add up, but it's hardly a nuisance. --- Nothing bothers me more than the fact that I didn't understand names should start with a capital when I made this account. PSN:Shimotto