Reading through the thread in my opinion the burden of proof is on the operator to prove they have reserves not on the users regardless of the percentage of funds held by users if the funds are all mainly held in a cold wallet the deposits would be in one address keeping the individual user balances relatively anonymous, and they can still prove their own reserves.
An absence of that does seem concerning and based on the timeline disabling investments was the logical choice next would be to prove they can cover large bets.