Those two suggestions use the Oxford comma because they are suggestions for how remove ambiguity while keeping the Oxford comma. The thing about just admitting

Those two suggestions use the Oxford comma because they are suggestions for how remove ambiguity while keeping the Oxford comma. The thing about just admitting you can rewrite a sentence to be un/less ambiguous while keeping the comma is that it simultaneously admits that you can rewrite a sentence to be un/less ambiguous without the comma... which puts us back at aesthetic arguments.