ExWrangler,
The only way I can even imagine this is for a very severe wrist rolling/turnover to take place in the swing versus palms up/palms down at contact; and then continuing during followthrough. Sorry, just having a real tough time visualizing this happening even choking up on the bat with a wristy swing. Is he trying to roll his wrists into contact?
Frankly have never heard of something like this. Not much help...any chance of a video?