Given the number of Xaela tribes (and the fact that the devs have said there are more than our canon listed ones), it makes sense to me that interior tribes are more reclusive and exterior tribes (especially trader ones or ones that have settled) are more open to outsiders.
I don't see a reason why you couldn't have an exterior or intermingled tribe hosting a more open event. Remember, for all the Xaela centric lore we got in the MSQ, there are still a ton of tribes and cultural nuances we didn't see. That leaves some wriggle room. And while not everyone is comfortable operating within wriggle room, you know, I think it's not going to break the lore to play in it now and then.
I don't see a reason why you couldn't have an exterior or intermingled tribe hosting a more open event. Remember, for all the Xaela centric lore we got in the MSQ, there are still a ton of tribes and cultural nuances we didn't see. That leaves some wriggle room. And while not everyone is comfortable operating within wriggle room, you know, I think it's not going to break the lore to play in it now and then.