As I, with affection, (like owning an ugly dog), or as I have posted, "a railroad tie with a grip" A proud Gen II G21 owner, I too was very interested in what the super dee dooper Gen 4 would offer for the G21.
I got the new back strap sizing options, dual guide rod springs,....but they kept the finger grooves.

IMHO, if it fits your hand, and you want one, just get it.
Either way, it is a pistol that has been beatin' , abused, thrown in the ocean, dragged down a gravel road, tossed out of helicopters, immersed in a bucket of mud, buried in the back yard for a year, filled with sand, shot crappy ammo, with worn out magazines, and still goes bang.
I drank the Glockenspiel Kool-Aid only after seeing the torture folks put this model through to try and break it. (Plus the 27rd. mags are always a treat to light up the range with.)....

It's an
all purpose pistol. If you take it to the woods, and fall in the mud, rinse it in the river and keep going. Raining? Snowing? Sandstorm? It's as good as your ammo. The firing pin will hit the primer.
No I'm still not a Glock super fan, as I do not like the grip angle or finger grooves of the G21, but the damn thing will go bang, when I need it to clean or dirty.
Looks like they reduced the prominence of the finger grooves,....let's hope that continues,....