Yeah, I hope this is a learning lesson for all. If it wasn't for the bad advice from Kohler, this would've been a more trivial fix. My gut instinct was right, it functionally didn't make sense nothing would come out of that hole. As stated, this is a critical function for flushing. In fact, with that now properly operating siphon, significantly less water comes out of the top down jets and overwhelming majority of the flush and fill action is coming from the siphon. I sent a note to Kohler with my original case and the before/after videos and an explanation that they shouldn't push back and advise customers you can't feel siphon action. Home Depot was stellar in taking the return, I do wish I tried this earlier.
Since it was installed on July 1st, this has been a major disappointment, and my wife thought we'd be stuck with this splash-back pee-spreading fixture forever. I can't state how elated I am now to use this, and it was fun to learn how all this works!
The one blessing in disguise here is that had I not gone through this, I wouldn't have ordered the 0.5 gpf diaphragm. While the 1.0 works fine now and siphons great, it's overkill amounts of water and extends the flush time and loudness of the flush. The 0.5 provides such a refreshingly short and quiet flush, so despite the bumps in the road, now I have what I think is a more ideally sized flush setup, and I save my bill and the planet half a gallon every time this thing is used
Thanks so much for the support.