UPDATE: I contacted Stone Age Gamer (the seller) and they gave me this response:
We listed systems that we got complaints about. It doesn’t mean it won’t work with those, we are just warning you that we received complaints about those specific systems. These adapters were originally created because Yobo made a Famiclone system. Instead of originally making a North American system they made adapters for it. That is what these adapters were intended for. Eventually they did release a North American version so these are left over adapters. We think the main issue is that the PCB is slightly thinner than a normal Famicom cart PCB. So sometimes it doesn’t make a perfect connection depending on how worn/bent the pins in your system are. Some people said by wedging something like a folded piece of paper in the cart slot with it made it work fine, some people with those systems said they have no issues, it just depends.
It may work fine on your system, that warning is basically a “buy at your own risk” kind of thing.
What I would like to ask now is: why would some specific revisions have that issue? It seems like the type of problem that should affect all revisions, not just a few.