It could of been the ceiling level that made them believe Cooper knew aviation? above 10,000 requires 02. also as 377 pointed out earlier that a lot of people haven't a clue with trim, rudders, and flap settings, but if one gains the fundamentals about them, he's good to go.
If we take note here with this whole discussion, another pattern surfaces. most on this panel believe it's possible Cooper wasn't a pilot, and now it appears the pilots are also the majority in this discussion against the statement as well. this doesn't make things a fact, but should be taken into consideration while trying to find some sort of background with Cooper.
I'm not 100% that he wasn't a pilot, but in the same sense I can't say he was. I lean more to Cooper gathering information with a lot of his statements. a criminal will case the area, it's possible he knew landmarks from his planning, and wasn't a resident as many believe.
This gets to the point of whether Cooper made it, or didn't make it. nobody can say for certain either way. we just don't have enough evidence to state facts about certain things. I believe this pattern follows a lot of things surrounding this case...