Agreed. Grip strength is just a proxy that’s easy to measure and doesn’t require the subject to learn proper lifting techniques. The point certainly isn’t to train grip strength.
It would be more meaningful to know how well one could perform lifts that support functional movements, but the data collection would be very difficult and poor technique would introduce errors.
I like Peter Attia’s rationale for training functional lifts:
Deadlift or trap bar deadlift and farmer carry so you can carry your groceries from your car when you’re old.
Do squats so you can squat down and pick up a grandchild or great grandchild.
Overhead press so you can lift a carry on bag into the luggage bin above your seat and continue to travel.
For that matter, train for VO2 max so you can walk up a hill and keep up with the tour group.