I quite take your point, if the taggants were not there, it would be entirely impossible for them to be useful. Yes, clearly, you are on solid ground there.
I am not all that knowledgeable about taggant technology, I cannot state with authority that they would or would not have been useful. Hence, “maybe yes, maybe no”. I don’t know, and, with all due awe, I am not convinced you do either.
Now, perhaps the NRA only offered opposition to taggants in firearm gunpowder, and specifically exempted fireworks gunpowder. “Oh, yeah, sure, fireworks gunpowder should be tagged, yeah, we are totally on board with that!” Seems unlikely, but if you offer me a citation to that effect…