Okay, I have an update on the recent copyright claim! The good news is that it was removed, with absolutely no effort on my part.
(I probably would have done something, but I didn't have Internet access yesterday.)
The bad news is that the exact same people slapped a copyright claim against my Nancy Drew: Ghost of Thornton Hall video, from the 2014 Mega Marathon. Again, they're claiming the visual content from an early part of the game. Since "wait a few days and see if anything changed" worked last time, I'll try it again!
UPDATE: The copyright claim disappeared! Great! I wonder if making the videos private for a while did something to reset the copyright claims...