I've never seen this until today. Obviously, I knew Hank had continued to mutate into his blue form (which they should have then left alone, without turning him into some cat creature). I never even knew he was gray for a while.
This was 1972. It makes me realize how much Marvel had dialed in by then (less than 10 years after it had all been created), and how much stayed in place up until 1990 or so.
Then, of course, it all went to hell. But I digress...
I've been wanting to read this for a long time. Haven't read this yet but this change makes sense, him wanting to fix himself, but Marvel keeps going back to the same well and having him change every few years.