Strange Replay Ruling in Yankees-Mariners

In the ninth inning of the Yankees-Mariners game there was a particularly strange replay ruling. The play on the field was ruled a home run and there was a runner on first base. The umpires deliberated and ruled that it was a double and that the runner from first base should score. I don’t see how this makes any sense at all.

How can they assume the runner from first would score? If you go back and watch the replay it’s clear that the runner was rounding third as the ball came into the infield so how can the umpires assume the runner would’ve scored?

If I were the umpire in this situation I would’ve awarded each player two bases and had runners on second and third. This has to be the call in this situation because you can’t assume the runner would’ve scored. The play had been signaled a home run and the runner from first wasn’t running hard so none of what happened during the play after that should be taken into account. If baseball’s interpreted like this then a ground rule double would always come down to a subjective call of whether the runner from first would’ve scored or not.

I’ve tried to research whether there is any precedent ruling like this and could not find anything. It seems like if the MLB put a replay system in place they couldn’t possibly just let the umpires subjectively put runner where they think they would’ve went. That’s a stupid system and the ground rule double rule completely contradicts it. I thought it was incorrectly called and I think we’re going to see a lot more calls like this made as the MLB (hopefully) incorporates a rational replay system.