Last year, with each of my seed heads bagged in Agribon-AG15, the top of the stalk (with the bagged head) was cut off the remainder of the stalk and a wire "hook" was wrapped on the bottom. The leaves had been primed of all but the top 4 leaves by that time. The heads were cut when most of the pods had turned brown. The bagged heads were hung (upside down) to dry for another month or three.
Some seed (maybe a couple of thousand seeds) spilled spontaneously from the drying pods, but a good size seed head will have a quarter million seeds, so this was insignificant. Once the pods were adequately crispy, they were broken into a pair of stacked sieves, with a 600 micron sieve nested on top of a 400 micron sieve, both situated on top of a 5 gallon bucket. The vast majority of the seed would not come out of an individual pod until it was crushed. Debris is trapped by the upper sieve, while the 500 micron seeds fall through, and are caught by the 400 micron sieve. Dust and under-size seed falls through the 400 micron sieve into the bucket. The good seed is what is kept in the lower sieve.
So, yes, seed will be lost from the inverted, drying pods, but not enough to warrant a second thought. Leaf-primed plants still produce abundant, viable seed. The longer the pods can mature and dry out in the field, before cutting the heads, the better the yield of seed. Cutting green heads, even if later allowed to thoroughly dry, my not mature the seed well.
Bob
