if you treat them as employees then the less productive employees (the walk ons) will not get paid the same wage as the top performers.
No one made you walk on to the team.
But according to the Northwestern players this is all about safety and medical treatment. They put themselves in harms way and they don't benefit financially. By this logic the walk ons and players who don't play are just as much entitled to compensation as the scholarship players since they put themselves in harms way during practices.
And without the scout team players the team either has to prepare without a scout team or use scholarship guys who play as the scouts. Then the walk ons could create their own "walk-on" union. They would say either pay us the same as scholarship players, or find another way to prepare for games!
I am just illustrating why this unionization is a bad idea.