Another reason the hotel was wrong and the groom was probably annoyed - the morning after brunch is a real possibility. Even just an informal one, in the same dining area as everyone else is not unusual, just like the pre-planned, perhaps private room or reserved tables brunch. I know for example my future in-laws are staying at the hotel we blocked and have sent out an email just a few days ago to their family, and asked DF & I to forward to any of our friends and my side, to say lets all meet in the hotel restaurant for brunch the morning after the wedding. This email was to all staying in the hotel, but also to people who live in the area (so a lot of money for the hotel restaurant!) You being at a different hotel makes you joining less of a reality, whereas if you were in the hotel with them, you'd easily be included if there is any morning after event.