What I had meant (but in re-reading what I wrote, I see how i was unclear) was that you can buy from swan and withdraw the btc immediately. If there is a custodian there holding them for those 90 seconds, or whatever, then I guess yes, a custodian does temporarily hold your btc funds.

I suppose I also didn't consider the USD held, waiting for the deposit payment to clear, as funds held by a custodian, but I presume that in another instance of exposure to a custodian, with Swan, that you cannot avoid.