Well I thought I answered that in my post above the one you quoted. It depends on his experience, if any...
And it wouldn't take opening it, the packed rig would be apparent. Mains are generally bulkier than bailout rigs, the container design is often a bit different, on mains the ripcord is usually on the right side whereas on bailout rigs they're usually on the left, mains have the D-rings, bailout rigs don't, mains don't have seals or packing cards...
The NWA or FBI people procuring the rigs probably don't have any idea about the differences, they're just grabbing what they can get. When they tell Emrick they've got the backs, he probably knows they've got bailout rigs, but he probably doesn't say anything lest they ask him for more. Which again, might explain the dummy reserve. There's no way in hell Emrick doesn't know that training aid from a real one.