The same now applies to penalty areas. Touching sand in a different bunker brings it all into line. The exception for touching the sand in the same bunker is because there is an opportunity to test the surface. Which in a bunker is likely to be more consistent than a PA.l
So if a bunker is treated differently to a penalty area in that one regard, why not just leave it as it was and be different in two points?
Or even allow the touching of the surface in a bunker to "bring everything into line".
You can test the surface anyway with your feet in taking your stance.