Why would my sons father lie about him being potty trained???

So my ex and I share 50/50 custody of our now 5yo son. He’s been potty trained since right after he turned 3. He’s always had to wear a diaper at bedtime though. Boys wet the bed longer than girls on average and it’s completely normal. His dad does not believe this and will get mad at him for it. I’ve even brought him things from our sons pediatrician (ex has never been to any appointment himself) clearly stating that it’s normal for a boy his age to be wetting the bed after being potty trained. So after son turns four ex tells me son’s pretty much stopped wetting the bed except the occasional accident. Great! Only thing is that is not the case at my house. So what’s the difference? I’m comparing with ex and we seem to be doing all the same things so I can’t make sense of why he’s completely potty trained at his dads but not at home with me. So then yesterday my son tells me that he wets the bed all the time at his dads house and he doesn’t know why his dad says he doesn’t.Why is my ex lying about our son not wetting the bed?? It’s normal for a boy his age!! via /r/Parenting https://ift.tt/2P1dZFe