If people send you money, you have to play it, rather than w/d?
That's fair enough, they aren't a bank. And transfer withdraw would be an obvious method of money laundering. They probably shouldn't allow it at all tbh.
Forcing play with deposited money does seem suspect given recent UKGC comments, but then again they could presumably just say ok we will give you the money back, but then we will close your account.
There are some on betfair who claim that they deposit/complete withdraw every day. Frankly surprised that they haven't been told to gtfo.
some accounts which have done this and similar have been shut in the last six months by betfair