This issue is still happening on Monterey, and Xcode 13.1

No, if anything it's gotten worse.

In the same boat. I tried 13.2 beta 1 and the issue still happens.

FB9727174, and I included multiple samples of the runaway swift-frontend process

I just tested this (13.2 beta, monterey) and it didn't work for me. swift-frontend still chews up all available memory.

Would that be OFFER_REDEEMED from https://developer.apple.com/documentation/appstoreservernotifications/notificationtype with a subtype INTRODUCTORY_OFFER? If so I don't see that in the the docs. I also don't see "OfferType" anywhere, maybe I'm misunderstanding.