What signals sent by author lists

I recently had a conversation about ordering of author lists for papers. Of course, each field has its own conventions but as people start publishing in multiple communities’ venues things can get a bit murky. There are pros and cons and different people have different values, etc.

This is all standard and has been hashed to death.

But what happens when you merge two papers with different author lists? Alphabetical makes things very easy, but if you go a different route, then the primary authors have to slug it out to see who gets first author credit. To split the difference, you could put a footnote saying that authors are in alphabetical order. In the conversation, it came up that putting the footnote implies that there was some tension between the two author groups and so this was the compromise solution after a debate. That was new to me: is this the correct inference to make in most cases?