It's not JUST the drum mapping that matters nowadays, as well.

You take most modern arrangers' drum SOUNDS, and a kick or snare etc. can have up to four or more different samples as you play louder. They can be quite different, for instance, many Roland snares add a rimshot hit to the last 3-4 velocities, or a pronounced 'click' is added at the highest kick drum velocities. This is what real drums do!

But there is no standard for at what velocity these samples change at. So a Yamaha multi-vel kit Part, played on a Roland multi-vel kit can sound QUITE different, as the accents either don't happen, or happen to much if they straddle the vel-switch at the wrong level.

GM/GS/XG made things SO simple back in the day, but as realism ramped up, unfortunately, the manufacturers didn't get together like they did for GM/GS (mind you, most of that was Roland doing it and everybody else just jumping on the bandwagon) and standardize these vel-switch points.

Sure, our modern arrangers sound quite amazingly realistic. But at the cost of loss of standardization, sadly.