In his case it does make sense to not custody keys. He’d have one giant target on his back. Not that he doesn’t have one now, but at least it reduces personal safety risk. 

I wouldn’t be surprised if he has a hardware wallet for a private stash. 

The last thing Saylor needs is to bring that wrong kind of attention to himself. 

all that being said I don’t know how he sleeps at night knowing it can all be taken away with one phone call.