Catching to be a better P makes no sense. My son caught and P until age 13 when we saw that catching was a contact position at times so we had him stop because his P abilities were better and didn't want to worry about injuries, which he had a few minor ones.
son also moved from SS/3B to outfield when not P which he loved. He got in the long toss he needed.
With 5 catchers in program how much playing time would son get? The fact that he can play Inf positions will get him more time.
My son is also a 2020 8th grader, who pitches and catches. He says that being a catcher has allowed him to be a better hitter. When you call for a specific pitch and you see it over and over again, how it moves, what the pitchers arm looked like, the spin...etc...well he swears it allows him better pitch recognition and he does have the lowest strike out percentage on the team...so he may have a point.
I will say that getting into catching in 8th grade is going to be difficult. Catchers have to move in ways that are contrary to how people normally move, and it usually takes years to get use to it. When you are a SS fielding the ball you can go with the flow of where the ball takes you, when you are a catcher trying to block the ball you have a split second for your brain to tell you how far to slide, how low to get, how to fall for the block. I have seen my son have to slam down to the ground on his knees for one pitch, for the next pitch he had to jump a foot in the air. This coordination of how to move your body is not an overnight thing. It takes years of repetitiveness and you have to think about 1000 things as opposed to the 2B who only has to think of 100 things.
The catcher needs to be possibly the most athletic kid on the team. He has to be a true athlete with quick reflexes and not just be quick because he is little. If he really has a passion for trying out the position I say let him, maybe when the team is up 15-0 in a game the coach will let him have a shot, but borrow someone else's gear, unless you can drop $300+ on your kids whim.