Disc Brake Conversion Failing

I don't see what the big deal is...or safety issue is. The two are obviously different [ from different manufacturers? ] & the shape is different. It is how they operate that is important. While the reservoir divider position is slightly different, the fluid volume that each section contains could be the same or very close because the internal shapes are different.
The big deal is that they sold me a MC that is supposed to be for a manual disc/drum application and it is actually a manual drum/drum application. I already had a perfectly working drum/drum manual MC and didn't need another one. The car is now set up for manual disc/drum so I need an MC to fit those needs.