Yes, it doesn't seem like it actually works super well. Love the idea though. I would probably pay money for a thing that did this accurately.

Personally, I think it's a feature that Em looks substantially similar to CM7. If this was all working fully as intended, I suppose you might get a clue from the darker-colored bass note.

A bass player probably has a different perspective, but as a keyboard player, it's pretty much always fine to play an Em over a CM7. It's just a "voicing choice".