I'd guess that it's the same with most/all custodian services. I see no reason they would share info about their internals. Every bit of info they share may be exploited by somebody sooner or later.
And that's why you should use a proper wallet instead of a custodian. Install a wallet, backup your seed or private keys safely and you are the master of your money.
Of course, you should install a wallet with public source code, so you can see how it operates