There is such a thing as osmotic pressure. While I can’t explain it well, I understand the concept. There is so much sugar that the yeast can’t survive and therefore it never even starts to ferment. here is a great podcast explaining high gravity beers and some explanation of osmotic pressure...
As for the orifaces, I just drilled mine out. i do forget what size but I googled it. Since NG is so low pressure, you need more of it so the larger hole fixes that. The air/gas mixture ring did need adjusting. I have been on NG for years now. I had a ball valve on the hardline in the house and...
This is an old post but today I was researching about this topic as I had 8 oz of yeast in my blowoff reservoir. I have a 1.086 beer and the activity was intense. Getting that down to 1.012 or less will need all the yeast it can get. I started with 2 dry yeast packets in 3 of 12 gallons of wort...