The private wikis of WMF are needed to record data of positive and negative nature, and the global title blacklist and global spam blacklist may contain data that needs to be recorded. ArbComs, Checkusers and Stewards are groups that specifically have a need to record data that may otherwise be blocked.
|operations/mediawiki-config||master||+20 -9||Exempt private/fishbowl wikis from the global title blacklist|
It was the title blacklist that is the issue, and I guessed wrongly then for spam blacklist.
For title blacklists, yes all of them. Any title will be purposeful on a private wiki and for the people using these wikis the likelihood that it would be abuse is insignificant.
Personally I would just schedule the patch for deployment, as I don't think those objections are worth worrying about, but there are no more deployment windows until 11 January, unless you can convince @greg that this is a high-priority request...