Why can boss fights be started while first-timers are watching the cutscene?

[Callinon]

If you do that, not even 1000 soldier bonus would be incentive enough to get me in Praetorium or Castrum again - and i'm probably not the only one.

I don't know... 1000 bonus soldiery would probably convince me to sit there an extra 7 aggregate minutes while the cutscenes play.