This bug has been fixed, confirmed, and deployed already.
If anyone's interested you can see it in the following commit-
https://github.com/vahnj/mastodon/commit/6b7ee3076860236a258f7bd7a50b5b822aaf803d
Somehow in rebasing changes, the placement of where we call a single new AllowDomainService (a service to abstract between blacklist/whitelist) got put after where we check whether we allow domains or not.