AIO for not getting exclusive bathroom access while visiting family?

(Posting from my husbands account.) While visiting my sister for a long weekend, she told us (my husband and I) the bathroom down the hall from the guest room "is your bathroom". Also on that hall is her husband's office, and apparently, that's his bathroom when no one is staying over. All weekend, he popped in to get stuff, used the bathroom, etc. I feel like for privacy's sake, he should have asked first. My husband feels that while the gesture is nice and appreciated, the expectation is too much. Am I overreacting?