You *are* talking about some design fix. When blocking was added as a feature, it was only integrated with some actions - it was checked during editing, but not during unblocking. That was an oversight that has started causing problems now so it's being fixed.

Even our largest wikis only see about ten self-unblocks a year, most of which are unblocks of self-blocks (which are not affected by the change). By no sane definition is this a major change. Had it not been announced here, no one would even have noticed it.