The problem isn't 'fragmentation'. The problem is that some hardware can't handle the way they wrote the code. They are going to write a version that uses less processor power and release that as well.

If they had written the 'lighter' version first, it would run on all devices.

Nobody ever talks about the PC market being fragmented, and yet it's nothing but fragments. It's difficult to find 2 PCs that are identical unless they were purchased at the same time. That doesn't stop developers from making apps and games for PCs.

When they say that 'fragmentation' prevented them from reaching the whole market, what they're really saying is that their software uses too much CPU or another resource.