That's not what they are doing. They only had three teams last year. They now have a bunch more, and have had a tremendous surge of kids wanting to try out.
So asking kids to bring their practice jersey from last year, will make them have a better chance to make the team? If the coach thinks a player should make the team that was with him last year, do you think it matters what jersey they have?
Epitome of ignorance.
Your looking for excuses why your kid won't make a team or from another group looking to hate.