I'm well aware of the differences and issues relating to the GBA expansion packs. I've already got a 3-in-1, and I'm looking for a cheap 32MB cart that will be supported by future versions of GBA ExpLoader (if there are any), and the M3 expansion won't be. If I had an M3 Real I'd certainly get an M3 GBA expansion for the extra features, but with GBA ExpLoader it's nothing but an eWin pack without 1024 kbit flash save support.
I guess this cart just had a single production run. It's too bad, because it's cheaper than the 3-in-1, and simpler to use do to only having SDRAM and no NOR.
Thanks for the info.