[mbyron]

Kallix, F1 does not have to separate his hands before throwing home as a fielder. He can legally step off and throw home to retire a stealing R3 without separating his hands. The rule you cite is intended to prevent the situation where F1 steps off, fails to separate his hands, steps back on, and pitches. This is a quick pitch. In other words the hands must separate before he pitches again, not before he throws.

Seems to me that Jim Joyce made a straightforward application of 8.05g. Mendoza stepped off and pitched. The motion was the same. You could try (w/ Francona) to make the case that he's allowed to throw to any base when not in contact, but his motion was a pitching motion and he had no reason to throw to home (a reason is not required by rule, but it would have helped Francona make the case that he was throwing home rather than pitching).

I liked the call. I would guess that Mendoza got stuck between doing two things: stepping off to freeze the runners (he was worried about R1 stealing), and pitching. Alas, he did both.