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

[Duuude007]

What/Where is this Inn?

I don't care too much if people kill off trash mobs but OP was outside the boss area and was locked out when the encounter was started. I think most of them are like 15 secs. A lot of the story mode main quest line cut scenes are longer than that.

There are three inns, accessible via the innkeepers in each city's Adventurers' Guild.

The lockout policy for bosses (once engaged) is exactly 15 seconds (according to the popup), which means 15 is enough... that said, if an agreement is made at the beginning of a dungeon, as the GMs suggest, such a thing shouldn't be such a surprise to any involved.