It seems it couldn't be mere coincidence that the $250K threshold matches the FDIC limit... maybe they have private insurance that's set up to match the same expectations as a fiat bank... or maybe they just figure that someone with more than $250K would be willing to pay more because they perceive it as better than the uninsured fiat alternative.
BTW, this just sounds like a lie (at least, it's grossly misleading):
"You have full control of your bitcoin (not a custodian)"
Sorry, having to rely on 2 entities other than yourself to sign any of your transactions can't reasonably be considered 'full' control.