yes and no
the KK does make it easier for beginners to achieve if not straighter throws, but longer spin times and more stable feel.
it’s very important as it allows the player to focus on nailing the technique rather than keeping the spin alive.
of course, you will have to make up for this shortcut later on, but at least you don’t get as frustrated and it will make it significantly easier for beginners to land more advanced tricks early on.
After that and a few months, the player will have developed a straighter, stronger throw that will allow him to appreciate the difference between various yoyo specs and various bearings.
I know lots of people who started on KK, some keep using KKs after years and are doing very well. Myself, I never refrained to use KKs and I still do on some of my throws, specially for 5A. But this doesn’t mean that I don’t appreciate flats, some throws are just plain better with flats.
but I can now easily switch from flat to KK without noticing a difference in spin times or stability, KK allowed me to keep making progress while taking some of the frustration away, leaving room for more fun overall. Once the progress is down, KK or not, your throw will become better, straighter, stronger and then, there would be no other point of choosing between flat or KK than your own personal preference.
the only wrong way to play with a toy is the way that gives you more frustration than fun.