147,
It has no grounding.
This fallacy is based on 2 Pesukim in Parshas Ki-Setze:- 1) Gedilim Ta’aseh Loch etc., immediately followed by the Posuuk of 2) Ki Yikach Ish Isho etc.
Hopefully, when you called it a fallacy, you were unaware of the fact that it’s a Mahari”l and a Magen Avraham. The Mahari”l is quoted in Baer Heiteiv and Mishna Berurah (O.C. 18, 4 and 10, respectively). The Shyarei Knesses Hagedolah calls it “tamuah”(puzzling), not because of the order, but because we would expect even an unmarried person not to be batel from the mitzvah of tzitzis. It’s likely that we, who make a brachah on a tallis katan, would have no such issue. Since even unmarried men do wear a tallis (katan), they are not being batel from the mitzvah of tzitzis.
The M”A is in O.C. 8, 3. He says that the Gemara in Kiddushin (29b) implies that unmarried men did not cover their heads with a tallis. Baer Heiteiv argues.