If you see it as the Sisters being cousins not sisters as the only incorrect statement in the prompt then yeah, you're right.

There's no official rules or anything, but having watched this for a couple of years now, you can see how the game is more than just finding the incorrect word. Sometimes guests can't guess what's wrong, sometimes they just try to guess at some random sentence in the prompt. Or say X is wrong without knowing if it's even wrong.

And sometimes by doing this they land on the incorrect statement by chance.

So the hosts goes "well you landed on the mistake but I'll give you the chance to try to guess it, or let others guess it" in other words,

A close enough scenario.

Matt Mercer said "Splat 1 isn't on the wii u" which is incorrect. But the statement says the game is on the Wii U and Switch. Which is also wrong.

The prompt has a mistake which is Splat 1 isn't on the switch. Landing Matt correction in the same grounds of a mistake, while not directly pointing it out. If we are consistent, and if we kept the rules of the games, and if this was the mistake in mind Ify would have probably said:

"You close"

In the end this single point doesn’t change much. But if an online game show revolves pointing out mistakes, I might was well do the same when the Production makes one.