I am not a chemist,nor do I understand how or why TSS works.Heck,I don't even know how the bacteria I have in all my tanks got there.I have just been stating things I was told along the way,before,during,and after I used this product.It worked for me.And somewhere along the lines,I was told it is a waste of money to use it while doing a fishless cycle with ammonia.Who told me that,I don't know.I have been searching forums trying to find it.All I am doing is passing along information I heard somewhere.
It sounds unreasonable to me that you are not supposed to use it in this manner,and I have the same doubts about it not working in a fishless cycle,like you said,ammonia is ammonia,but I have never tried it in this application.But I also would not want the OP to waste his money on something,when I was told it won't work that way.
When I added it to a tank that had the cycle crash,with fish in it,it worked just like it was supposed to.