How do you know the pollen is sterile?
Real world and research. The dep I treated I ended up removing all pollen sacs by hand after the first application. Didnt have patience to wait. A moderate amout of pollen was released during that session.
I continued to treat weekly in the hermie dep. But not manual removal of pollen sacs, but still some would sneak thru and open. There was tiny tiny white empty "seeds" in the older calyxs but nothing more mature than that. Likely from the very first nanners before the first treatment. I would even take buds during flower and break them down looking for seeds, fearing beans in the duff of a turkey bag. But never found any.
I harvested the 2nd dep, which wasnt flipped till the 3rd florel treatment in the hermie dep. It was 3 feet away, both deps with sides up. This run did not need florel. No seeds were found drying, bucking, or trimming out of the second dep house. Not even the little white ones when rolling a joint.
Empirical evidence is not enough for me at times when I dont understand it. The literature and research published of using ethephone said that in some crops sterility of the pollen may happen among the other things it does to plant flowering processes and embryo development.