I'm not trying to defend Saylor with this question....
But, what he's calling yield on Bitcoin isn't really yield on Bitcoin. Right? 
I mean, to generate a Bitcoin yield you need to lend your Bitcoin to someone who pays you for that lend. No?
He's just taking on more debt through MicroStrategy in order to buy more Bitcoin, and calling the rise in price of Bitcoin a yield, instead of an unrealized USD profit.