There’s still waffling in his language in that longer transcript. He’s not admitting that he was going to call it a strike (even though he clearly was), just that after looking at it again he can see that it was a strike.
Balls and strikes are a judgement call, whether the batter tried to get out of the way is a judgement call. The Marlins really only win a protest if MLB rules the umpire was going to call it a strike, but gave the HBP instead.
It does happen in rare cases and this one is close to that line, so there is a tradition of being able to do this.
By my count, 7 of the 15 successful protests overturned rulings by the umpires on the field. Including once in 1943 over a very similar issue. (The rest are protests of rainout and called games type things)
August 21, 1979 Shea Stadium, New York City
Houston Astros 9th (top) New York Mets
Umpires disallowed a single by a Houston batter that had occurred with Mets’ first baseman not on the field.
Initial Result: Mets 5, Astros 0
Final Result: Mets 5, Astros 0
I’m still thinking there can be some relief here. Mattingly files a protest, and Kulpa agrees that he thought the pitch was a strike and applied the HBP rule incorrectly. It’s worth a shot, IMO.
Maybe I got my wires crossed with football, where I can recall a couple instances of a game-ending bad call having a direct binary effect on the outcome (i.e. changed the winning team) and the conference/league admitted the call was wrong, but the outcome wasn’t overturned.
Looking through the list of successful MLB protests that caused a resumption of play that weren’t related to rain delays, it’s only happened once in my lifetime.