Witherspoon still gives pointers on it on his channel. Archie Moore wrote an extensive piece on how his system works, but most young boxers and even most coaches won't bother reading through old manuals and articles. The problem is so many legendary trainers are dying out before they can pass on their knowledge and understanding of the sport. Attempting to look at footage and figure out how things work is kind of like reverse engineering technology or looking at fossils and speculating how an extinct animal might live.
Anthony Joshua would've benefitted from it hugely when he was younger since he refuses to move his head and has big arms and shoulders. I'd imagine he'd have fewer KO losses if he has learned to use his crab shield to absorb and deflect blows. The trade off is Joshua would have a harder time using his otherwise good jab, but a good coach could've fixed this.
It is interesting that both George Foreman and Max Baer adopted this style, when they were slowing down.
As reflexes diminish it’s far easier to cover up than to try and slip punches or do single arm blocks
For sure, but they would have had other options for doing so style wise. They both found that to be the most appropriate adjustment, probably because it works on the front foot.
