I think the sulfites have built up on the bottom of the plates and the alleged cleaning and wrincing washes it away. Still seems like an effort in futility.
Not sure how legit it is, but I had a similar experience with an AGM battery in my 4-wheeler. The dealer claimed it had a new battery installed when I took delivery. Even early on it struggled to start at times, but would crank forever just fine. Also threw the power steering fault code all the time (even with the engine running). After it sat unused for a couple of seasons, I researched a ton while looking for a good battery charger / maintainer and settled on the PulseTech XC100-P
Since the battery had been sitting for several seasons it was only reading about 8.5 volts when I removed it from the wheeler and attached the PulseTech Charger/Maintainer. 8.5 volts is WAY below the minimum 10V of a discharged battery and I was concerned the PulseTech would consider it a bad battery and give up. However, it kept pounding away and gaining ground and after a couple of days it read "100%". I wasn't sure if it was completely done de-sulfating, so I called PulseTech. They recommended leaving it attached to the Charger/Maintainer for about a week. I think I actually left it for 3 or 4 weeks. Afterward, the resting voltage was right around 13V. I tested the resting voltage again after 2 months sitting on the bench and it was still above 12.8V. I put it back in the 4 wheeler and it starts right up, and has not had the power steering fault ever since.
I actually use two of these Charger/Maintainers now so I can rotate them between the 4-wheeler, the Vee2, and the cage (since it sits for weeks at a time when I'm commuting on the Vee2).
Interesting story about the battery in the cage. I have a dashcam that records while parked. This of course taxes the battery because it discharges a bit more than it should. Even though I will drive it for an hour at a time to charge it up, it will progressively get a weaker and weaker start cycle. Until eventually when I get in the car it says "System shutdown to conserve battery". It always starts, but once I get close to or receive that message, I hook it up to the PulseTech for a couple of days and it is good to go again. I wish someone offered a reasonable AGM battery that would drop in for that thing, I'd buy one in a heartbeat. As it is I'd have to modify the battery box, or buy the one and only current direct replacement option that is about $450 (cheaper to just abuse the stock battery - I can get 4 of them for that much coin). Which I don't understand for two reasons... 1) Ford uses that same battery in a zillion cars / trucks / etc. - the aftermarket should be all over that! 2) Why is a modern new car (and zillions of others) furnished with a battery technology from 50 years ago? It is not even maintenance free! Yes, I have to pop the top to check and add distilled water... Come on, where's my AGM? While not necessarily an actual deep cycle / starting hybrid battery, at least the AGM would handle the minor discharges from the dashcam better than the stock battery.
The PulseTech is a bit pricey, typically about $70. But it has paid for itself already by restoring my neglected / abused batteries that would have otherwise required replacement. However, all of this will only help an otherwise healthy battery. It only claims to remove the sulfates, it can't restore used up lead plates or fix bad internal connections.