I think this logic falls apart if you realize that wikis only "work" when you're able to get some of the readers to turn into long-term contributors, and losing 90% of your traffic by not showing up on Google is a great way to kill that funnel.

There's a ton of historical evidence of wiki migrations (1) starting out with all of the editors and none of the readers, (2) not doing anything to get those readers to the new site, and (3) ultimately losing the whole war because the reader->editor flow was still happening on the Fandom wiki. "Invisibility" is absolutely not desirable here, even if your only goal is maximizing the amount of good contributions.