Because that is an inconsistent hierarchy, which makes the code broken, and leads to bugs.
Bugs come from the MRO and previous solutions to it. Which i'd argue come from the obsession on that idea that ordering is the way to go. it is not. A solution that can resolve method in what you call inconsistent hierarchy would make those hierarchy not inconsistent anymore. I think that's a non argument, or maybe it shows that there's no proper full solution to multiple inheritance to this day. But think about it, would you call that inheritance tree inconsistent if somehow there was no resolution issue? Of course not. It is only inconsistent within the current MRO system. I'm aware of some of the evolution of those MRO algorithm. I know that previous iteration were broken in some weird cases. You'll notice that my solution behave exactly like the current solution in case simple inheritance, and that i've tested it thoroughly in what i assume is all the possible cases, given the set of rules i decided for my Explicit Method Resolution. Feel free to take a look at it here : https://github.com/malmiteria/super-alternative-to-super and let me know if there's any of those weird scenarios you can think of that i missed