There should be no reason for "frozen funds". You were sent funds and suppose to hold them. You either have them or you don't. Unless your system paid off too much you should have the BTC that was deposited, the players did not win against the house. Obviously this is not the case and you spent the BTC on something, why should you not be accused of scamming or at least stealing? You borrowed without asking by spending others' BTC.
One possible explanation is that for a while the new "invest" feature was treating new investments as profits for old investors, and so early investors were able to withdraw more than they should have been able to. Several people claim to have seen this happening. If it really did, then the site will have been left with a deficit even if they did later fix the invest code to work properly.
I'm not saying that is what happened, since I have no idea. It's just one way in which the site could be having difficulties honouring withdrawals without any deliberate attempt to scam. As
Hanlon's razor says:
"Never attribute to malice that which is adequately explained by stupidity".