Exactly this. Devil's work indeed.
Itch.io, in your update you state (bold emphasis mine): "We are currently conducting a comprehensive audit of content to ensure we can meet the requirements of our payment processors. Pages will remain deindexed as we complete our review. Once this review is complete, we will introduce new compliance measures. For NSFW pages, this will include a new step where creators must confirm that their content is allowable under the policies of the respective payment processors linked to their account."
There should be no issue sharing what, precisely, the payment processor's requirements are, or linking to the payment processor's policy documents (which should be public, right?). At the very least, communicating what they specifically asked be removed in this particular purging would go a long way.
But my suspicion is that you can't, because I doubt the payment processors HAVE clear content guidelines beyond content which is obviously illegal, and typically communicate what is and isn't acceptable in a similar vein to the Oracle of Delphi.
This smacks of, "I am altering the deal. Pray I do not alter it further."