I think UA's upgrade policies are more than clear. As much as I'd like to know the edge cases, I understand why UA won't really tell us. Upgrades aren't "supposed to clear". UA as a business doesn't want to upgrade somebody until they have exhausted every other opportunity to make higher revenue off the same seat. UA doesn't want to incentivize folks to purchase a lower-fare likely to get an upgrade over a confirmed seat in the higher cabin. Our status/fare paid/upgrade certs give us an opportunity for something that would otherwise go unused and most others don't have access.

The business reality is that UA has no reason to clear upgrade space in advance unless its for an operational reason (e.g.; make space in the current cabin to sell more seats). I would expect more and more flights to go battlefield or at minimum not expecting to clear until a day or two before the flight to minimize GA work and jeopardizing ontime departures.