Ignore this if you guys already knew about this.
If it's about gambling, why Coinbase just allows withdrawals? I believed that will be a subject for checking.
During my early journey in crypto, I involved in a group of Coinbase users in a social media group (during 2015-2016, Coinbase and XAPO are the most famous web exchange, at least in my own observation that time so I found that group) wherein some of them got account closed due to gambling. Coinbase didn't allow withdrawals easily and if I remember correctly, it takes several weeks to around month before those users got access to their funds. I believed those complaints are legit because they are really mad, disappointed, etc. but in the end, they still access their funds back. Coinbase also stated their violation unlike in OP's case.
I don't know if Coinbase changed its policy from back then (well 4 years later) regarding gambling-related cases.
But whatever it is, good thing, OP got the funds back and that's what matters here.
Likely things changes in the years and they have different kind of proceed for different violations,my deposit amount is just negligible compared to my overal deposits but its still against it so they closed,only good thing is I was redirected to account closure page to withdrew everything remaining in my wallets,no questions,no documents they just asked to go me to go away,bit harsh but its their rules so can't argue anything more on this.