I think its a requirement for guthans hosts tbh. So no, it doesn't mess it up.
It's weird because whenever I look up a guide fight arena isn't on there...
Does Fight Arena mess up the AFK Guthan's method?
Does Fight Arena mess up the AFK Guthan's method?
If multiple Bouncers spawn they can get stuck on each other, meaning it's possible you won't get hit and auto-retaliate, causing you to log out. All of the AFK Guthan's bosses are 1x1 in size to prevent this from happening.

