They left a couple retro reflectors on the moon during the moon landings so we can bounce lasers off them to accurately measure the distance to the moon.

I think that’s what they meant, cuz a ping to a radio device wouldn’t prove much, just that you are getting signals from up there. A laser would prove definitively.

Because there’s like 6 of em, and we know exactly which mission launched each one.

You are correct, it proves nothing. None of these things prove that people have been on the moon. Unless you want it to. Then anything is proof 😅