This is a video of my 850 demon carb, that shows the front squirt time is to short.
I had the same problem, although to a much smaller degree, with my 850 ProForm.
In the end i fixed the stumble on my ProForm by going from a 37 squirter in the front to a 28. Seams counterproductive but it worked. Would my 60 time improved more if would have went to a 50 cc squirter..........Probably. But this fix was cheep.
Go to the 2 minute mark, I did a slow mo if it. this was in gear with my foot on the brake.
Now I recall - you taught me that video trick!! It helped me when I was working to solve my stumble.
Your fix is not counterintuitive. You lengthened the pump shot with the smaller shooters to cover the lean hole until the main circuit could catch up. Pretty straightforward theory but takes a lot of trial and effort to get it right!