It's precisely what happened to me. You need to read that comment in context. It only refers to a person on a multi-pax PNR of >1 other non-elite. I can only assume those that cleared before me were not in that situation. Of course UA clears NF space and people get upgraded after check-in, that is well documented. But even though I was on the upgrade list and above other passengers (by UA's own system), when NF space was released, I did not get my upgrade in my PNR but others below me did. I can only assume that was because of my situation with other people on my PNR.