Respectfully, I believe you're unnecessarily overthinking this bailout vs. main thing and his reaction/non-reaction to what they gave him. I don't think we need to even go that far into it to find the biggest clue that Cooper provides us regarding the chutes. The most obvious clue to his experience with parachutes can be found at the very beginning: his demand. By simply demanding "two fronts and two backs", this tells us most of what we need to know about him, which is that he was almost certainly NOT a recreational skydiver of any sort. I've used the analogy before on my show, but if we substitute a getaway car for parachutes, Cooper essentially just said "give me a car" when he instead could have easily said "I want a Ford Mustang Shelby" or "I want a Camaro". Some just asking for a "getaway car" would indicate that this individual is not a gearhead in the same way that asking for generic parachutes indicates that Cooper was not a recreational skydiver.
Cooper's lack of specificity with his demand is so highly, highly informative. Every skydiver on this site and every skydiver that I've spoken to at CC's or on Facebook groups have been unanimous in stating that they would NEVER just ask for "parachutes" in such a generic way if they were pulling off a heist like this. First off, most skydivers we've heard from on this issue have agreed that they would bring their own chute if they could, and if they couldn't, they would be very specific with their demand.
Our two recreational skydiving copycats illustrate this perfectly. Heady brought his own chute, and McCoy both brought his own chutes AND was also highly specific with the parachutes he demanded be brought to him (four Commander parachutes from Perry Stevens' Loft in Oakland)
You stated that H demanded "fronts and backs". Mac requested "six parachutes". LaPoint said "two parachutes". Fisher simply demanded "a parachute." None of those men were sport parachutists. Cooper making a similarly generic demand for parachutes throws him firmly in that camp.
So I don't feel it's really necessary to try and figure out whether Cooper knew the difference in a main vs. a bailout because he's essentially already telegraphed to us what his level of intelligence was toward parachuting equipment from the very start: he lacked the knowledge to be specific, which strongly implies that he wouldn't have known the difference in a main and a bailout rig. If he had any real knowledge of parachuting gear he would have used specifics with his demand.