There are a whole number of variables at play that affect op-ups. Status is but one along with service recovery, targetting to change behaviour, past history, fare paid/fare class and at the last minute the type of seat needed.

That said I am still averaging a 50% J to F upgrade rate as GGL. Less 5% Y to CE on shorthaul.

I wouldn't expect a normal member of ground staff to be fully versed in that so describing them as lying is rather OTT.