Apparently the person at SAP who wrote that thinks that 12.5 is a maintenance release of 12.0.
If the 12.5 license allows running 12.0, whether that is a bug would depend on whether Sybase intended to allow use of prior versions when you license the current version.
If they are going to license maintenance releases separately, that is definitely something new. I suppose they want to make sure only users with a maintenance agreement can install and use maintenance releases.
We should get clarification from Sue.