From my past experience in related industries, the FDA/DEA wait for stuff to be fully illegal. What will happen is eventually something will occur which pushes them to schedule the peptides, SERMs, etc as controlled substances.
The loophole isn't flimsy at all; it is simply narrow. It has been used in a number of different cases over the past decades in the US. The huge downfall are websites that somehow suggest their products are for consumption. If they never provide anyone with usage instructions, never suggest consumption in any way, and generally watch what they say, they will be fine. The ones getting prosecuted are the ones who get sloppy. If you do RCs, you can't even sell to the one guy who slipped up and said something about consumption once. IP block him and flag the address/name/payment info in your system to make an on-record example that you don't tolerate misuse of your products.
Tony Huge from EA gets away with his "promotion" of human use because he is an attorney and knows his way around the laws so well. Now, THAT is cutting it close to the line. I believe the trick there is that he only reports experiences and never suggests that anyone take his advice. Additionally, EA as a promotion company is split off from the actual product sales company in some way. I would NOT try his promotional methods unless you, also, are a highly successful and astute lawyer.