No, they said it would help participation at the high school level. Little kids didn't and don't care about a singlet, a two piece, shorts or a t-shirt. They found declining numbers began in MS and mainly at the high school level and tried the two piece. The. NFHSSA created the option in 2017 - 8 years ago. College wrestling may not have been the target, but they were certainly used to try to mainstream the two piece. I agree that it didn't hurt participation, but it also has not been the factor that has increased participation. When it was introduced participation increased very slightly, then dropped off in 21-22 due to the pandemic. The biggest jump in HS participation in both boys and girls happened from 22-23 to 23-24. If you read a lot of the articles on participation increasing, it is due to girls wrestling (and football), parents wanting their kids active again after the pandemic, the increased focus on promoting the sport (Let's wrestle, Wrestle Like a Girl, etc.), and the increased work of youth and HS coaches to promote the sport. The two-piece singlet didn't hurt participation, but it was not the driving factor in increasing participation either. It really has been a non factor and just provided an option for some kids who want it.
https://www.vice.com/en/article/good-riddance-to-the-wrestling-singlet/
https://www.statista.com/statistics/268028/participation-in-us-high-school-wrestling/
https://www.themat.com/news/2024/august/20/nfhs-high-school-sports-participation-boys-and-girls-wrestling-make-big-gains-in-2023-24