It's uncommon. There's nothing wrong with it. It doesn't cause them to end up gay or trans (which is what you're really terrified of). Adults control that narrative, so if you want to encourage kids to bully other kids, by all means, be a pearl-clutching snowflake as you demand your sons conform to toxic masculinity stereotypes without the slightest trace of irony (and then call liberals snowflakes without the slightest trace of irony).
… I have girls no boys but if I am blessed with a son one day and he wants to dress up as a girl I’ll probably say no let’s not do that lol