Question

Hello, honored Rabbi. It is brought in Menachot 42b: “Rav Yehuda said in the name of Rav: If he made them from the thorns, from the threads, or from the scraps, it is invalid; from the sisin it is valid.”
“When I said this before Shmuel, he said: Even from the sisin it is invalid; we require spinning for its own sake.” Rashi explains there that their dispute is whether the rule of for its own sake applies only to the making of the fringes (according to Rav) or also to their spinning (according to Shmuel), whereas Maimonides explains that the dispute is only about the spinning, but as for the making, according to everyone it is not required. The reason Rashi explains it this way is that he understands “thorns, threads, and scraps” as situations in which the fringes are already part of the garment, whereas Maimonides understands “thorns, threads, and scraps” as threads considered waste material. Which interpretation seems more correct to you? That is, which explanation do you think is more implied by the Gemara (or perhaps another explanation altogether seems more plausible to you)? It seems to me that since Shmuel brings in the rule of for its own sake, it is more reasonable to understand “thorns, threads, and scraps” as something that is also invalid in the context of that rule, in addition. Also, it does not seem to me that the quality of the threads or their degraded state should be something that invalidates tzitzit at the Torah level, but only rabbinically. Thank you very much, and all the best!