Totally fine. Happens all the time. Just be clear about how you want your writer to handle it.

"I am only familiar with [version of canon], and I would appreciate not getting spoilers for other versions."

"I have only read [___], but I'm 100% fine with any kind of spoilers."

"I really like [___], so please focus on that and don't make anything from another version a pivotal part of your fic."

etc.