My worries are that the Supreme Court will say, "Well, technically the legislature didn't make these changes, but a state official does so that still counts as the 'legislature.'"

Yeah this is kind of the angle I was driving toward, because if it can be shown that enough states did this, they can probably make some kind of argument that "clearly this is considered standard operating procedure done without objection from state legislatures nationally, even among the states bringing this case, therefore there's not really any problem", or something like that.

The biggest concern I have about it is that while you're right it's not the only thing the case rests on, an article 2 complaint is by far the clearest in terms of giving Texas standing. If they lose that as a line of attack, the others might not be enough to give it to them (e.g. it's not clear that a state actually has standing to sue another state because voters in that state committed fraud)

I guess we'll see. I have to say though, regardless, it does cast the case in a rather weird light after I learned about that. (2 of the cosigning states even made changes to accept mail in ballots after election day in this fashion...very strange position all around)