I think what he means is if you back up a project from the A4 and a project from the Rytm and both are called “ProjX” for example, then they will both be called “ProjX.syx” with nothing to distinguish which file came from which machine. Appending an A (for analog 4) or an R (for rytm) will help avoid any confusion. And will also prevent you from loading sysex file made on rytm into an A4 and vice versa

To be honest this is not something I currently do either. But it’s a good idea and now would be a good time to start