Yeah, good point - the -1 helps with dips that are enhanced by PB scaling but doesn't solve the issue of other class-defining 1st level features being over-accessible to other classes as a 1 level dip. Stalker0's X levels in a class before you can dip into another feels far cleaner in addressing the source of the problem. I'm warming to 3 levels in a class if you want to keep them if you gain levels in another class.It would depend on what the overly good dip class abilities ultimately wind up being. We might not have the warrior group packet yet but imagine playing a level 11+ fighter eyeing that one level ranger dip for that no concentration hunters mark and one more skill and expertise on any two of your skills and two primal cantrips (the new reaction guidance & resistance are both primal nfor an extra cherry on top).
Whatever the fighter looks like when we get it that probably makes for one heck of a dip at those levels but is almost entirely unaffected by a -1 proficiency, two skills are actually four points higher than before. Imagine it was the other way around & fighter 12 gave a choice between +1 proficiency or all those other things when we get warrior group classes. People would wonder if there was some kind of extreme layout error & expect a corrected version to be uploaded by lunchtime.