I've never had any custom molded earplugs, but I could definitely go for some. I have a pair of knockoff Airpods, same shape and size as legit Airpods, and the left one never seems to want to stay in place, it always likes to fall out of my ear.
My guess is you may be talking about AirPod Pros that, like most of these wireless earbud types, have rubber tips that snugly fit in your ear canal, and he’s probably talking about the regular AirPods that just sit in your ear?