Though I was confident this was just a metaphor, I did try cracking a walnut using this method. I submerged three walnuts in a jar with some tap water, and let them sit for three years before trying to open them.

It was a let-down: they were easier to open, but certainly not by hand, I still had to use a nutcracker. They smelled bad, too. I did not try eating them.

I saw someone on You-Tube that soaked them overnight and then used Grandpa's Goody Getter nutcracker to open them. The shells shattered less, he got much bigger pieces, and it wasn't as messy. I have tried both with and without soaking them overnight and I agree that soaking overnight is better than not soaking. You still need a very good nutcracker. https://www.grandpasgoodygetter.com/products/black-walnut-nu...

It is a mixed metaphor, he refers to the problem as a "nut" but says after soaking the nut should open "like a ripe avocado"