the ball was struck by the bat, landed in foul territory, and then, untouched by any player, proceeded to roll fair.
by rule, that is a fair ball. the triple play was legitimate.
That’s my take as well.
The Dodger catcher made a real heads up play by going for the ball while it was still moving in fair territory. Had he allowed it to roll foul again, there would have been no play. What I found really amazing is that the Seattle players and the batter all froze after the ump made the fair ball call.
They would probably have been out anyway, but back in the 60's or 70's, the player would have been fined by the team for at least not trying to advance.
If the ball were ever “foul” on the play, it cannot become “fair”, or “un-foul” by being untouched by a player, etc.
I recognize that an untouched “fair” ball CAN become “foul” by rule, but you would need to explain to me how the reciprocal was true.
The call had to have been “fair ball” from the beginning for this play to be within the rule.