I don't see A16 referenced here. I still love your theory though!
But there are also a lot of unreleased iPads on the list that we know won't come out because they would already be obsolete. It doesn't actually guarantee an iPad 15,7 and iPad 15,8 will come out... there could be an iPad 16,3 and iPad 16,4 come out as the 11th-gen iPad instead.