The article itself stated that specifically training your grip strength won't magically give you better health outcomes - like you surmised, over-training that

The article itself stated that specifically training your grip strength won't magically give you better health outcomes - like you surmised, over-training that aspect breaks this metric. I think the causality runs the other way - untrained grip strength is a great indicator of a lot of useful things. Probably a good mix of neural and tendon and muscular stuff, not just a "let's go test a bunch of random people's flat bench press score and find out who's been hanging out in the gym a lot". Never tried the Iron Mind numbered grippers, but I have an Ivanko Super Gripper. I use it cautiously as years of Judo and BJJ have given me "high mileage hands".