Is it safe to boss outside of the regular channel?

Like Empress is only ch 12, I'm not sure why but it seems like we can go on ANY channel. How come its all channel now? Is it perm or an event related to those new exped. Or maybe its a glitch/a trap.

I don't see anything about being able to boss in all channel in the Notes.

It is because of the sengoku expedition event. It's to make sure everyone can get their boss kills in without worrying about overcrowding.