When T206163 is complete, the restrictions on overlapping partial blocks will be merged together and the user could get a block notice for a block that doesn't cover the restriction.
This can cause confusion if the user wants to know why they are blocked from a page, because they wont be able to specify which block it was that caused them to not be able to edit.
User has two blocks that are applied to them (ip ranges, etc.) one for Saturn and another for Mars. The first block selected is the one for Saturn but they are trying to edit Mars. The user will be prevented from editing, but the block notice that is displayed will be for the block that applies to Saturn