I agree with you on this, leaving a large balance as a bank roll will increases your chances of getting robbed on the long run just like what happened to the ops he was not guided enough or should I said he trusted that the casino will protect his money and privacy but reverse is now the case.
In the recent events were casinos either pulling and exist scam or getting hacked, it must be appropriate to avoid leaving large funds in the casino regardless it be bankroll or just your balance.
Even 5-10 units is too much. In fact, any platform carry inherent risk of account closure, kyc, etc. Really, it's unwise to use a centralized gambling service or casino, period.
I only say keep 3 to 10 units due since I try to account for Transaction Speeds/Fees from either BTC or ETH gas fees. oddly enough the only sites to ever close my account was B365 and Intertops.
Sadly few smaller sites ended up closing shop [Eve-Bet | 2012 - 2016] but at least given enough of a warning I haven't had to worry