It would honestly be a situation basis for me on what gym the child was tumbling at besides mine. Last year we had a family who came in and asked if they could attend open gym at another allstar facility because it was closer, and they could car pool with a classmate who cheered there. Her daughter was a level 3 and JUST (Im talking the day before) JUST got her layout and this was like a week prior to tryouts and wanted to let her daughter tumble extra because they couldnt make open gyms at our gyms scheduled times. We told them that it was fine, but that the gym they were going to progresses their tumbling entirely too fast. We warned her that if someone (meaning the staff) saw her layout, that told her to start working fulls, to say no. Sure enough, they came back in and explained that a staff memeber saw her (janky, because it was new) layout and wanted her to work fulls on tumble track.
Sometimes its not MY insecurities of my facility, but a true concern of the safety for my athletes. I appreciated the parents talking to us so we COULD warn them, and sure enough, we were right. We know our kids are friends with kids from other gyms, and its hard to patrol what they do. I think making a public statement about not allowing it sounds a little insecure, but thats just me.
If I were to send out an email in regards to my last gym (which I wouldnt, but just hypothetically), I would have addressed it in an educating parents on proper progression vs. saying youc ant tumble elsewhere.
ETA: Is MeanJ on their mailing list?