A judge who does this should not be judging this type of exhibit. Perhaps it's just me, but the fact that every item in the exhibit is a commercial usage should make it obvious to even a blind judge that an FDC does not belong.
While have seen judges make some shocking misstatements, here the judge was correct and not at all at fault, the exhibitor was for declaring there are "no known solo usages" when there are thousands--but none pays a proper rate. (Now when he wrote there is "no known solo $5 cover ** paying a proper rate" he received no further grief.) The same exhibit had first day of rate covers, first flight covers one of which was sent on a special one day only first flight route just to service the mass of philatelic covers BUT that philatelic first flight had the correct rate paid for by a solo 10 cent Prexie coil -- a rare usage. But few if any experimental helicopter airmail covers have even been shown since they can only be identified for certain by the philatelic cachet and don't carry a three or four figure price tag unless including the number to the right of the decimal point. Last example, while I generally don't collect Prexies, many folks want my FDC of one of the double digit values which paid the correct and quite scarce combination surface and air rate to several European countries.
** The closest is a single $5 stamp and a postal meter strip paying a correct rate.
If I were to write "'Crowd on,' the crowd chanted while dancing to the crowd." Then asked one to explain what was happening in the scene I described, few would quickly reply, a large group of folks dancing on a sailing ship to the music from a stringed instrument while encouraging more sail to be added to improve wind catch.
How often is leap year? If the answer is every four years, you are 99% correct. When I get blow back I point out the one who answered is willing to accept a 1% error rate.
If I ask how many leap years are in a century and the answer is 25, I point out they accept a 75% error rate as only one in four centuries have 25.
Remembering the divisible by 400 leap year rule, from 2000-2020 how many years have 365 days? Answer, they all did. Now six were leap years with 366, but each had a 365th day.
By your definition there is no such thing as an empty glass (outside of a vacuum), but you are the one missing the real picture as no one cares how much air is in the glass.
Just because a group does not care about facts and reality, that still does not make their answer correct, it just means they have no concern about being correct and thus one can better evaluate them as humans and the need to dumb-down. Heck some schools now give part credit is you answer to how much is 3+3 and your answer is 5 or 7. Expecting a correct answer is no longer politically correct.
When confronted with such a low brow example, about the glass, my immediate response is a request for a point of clarification, "which half are you discussing the liquid or the air?" That usually knocks them back on their heels and more importantly gets them to think.