NFL takes the responsibility of testing/clearing supplements, et al then the company comes in for huge fines/bans if they change formula without telling anyone (nfl, players, public)
Heres a list of NFL banned substances: https://www.nationalfootballpost.com/columns/features/nfl-banned-substance-list/
I do think that the NFL should have a list of supplements that are tested. Or players should have the ability to have supplements tested (ideally at the cost of the manufacturer. But ultimately...the players are still going to try to gain an edge and many of them will lie that they took an NFL approved supplement. These supplements are always evolving and there’s a reason why players are getting these exotic supplements that they “didn’t know” has a banned ingredient.