I generally prefer to match our chapter releases to the volume cover of where it was found (i.e., if it was a chapter from Volume 2, then it should also reflect Volume 2) but because we're quite literally paying for chapter releases every month before it gets smooshed into a tankoubon, we don't have access to the third volume's cover until AFTER the chapters are released. So for Volume 4 you'll see the Volume 3 cover, and so on, etc.
Anyways, I'm glad I could finally see what the hubbub is about with the volumes. I didn't want to assign volume numbers to the chapters until after I could see the finished Volume 2 so I can figure out the pattern.

As always, thanks for reading and here's the meme we made in the afterword.