Sounds like a boatload of crap to me...
Really, the only time you have to worry about that sort of stuff is if you have an eckie that is prone to toe tap...
And the real danger is that people get supplemented pelets, and then unnecessarily add vitamins ON TOP OF it which is both expensive and stupid, and could in rare cases lead to toxicity...
In all my years, I've never seen a bird who got vitamin toxicity from eating too many pellets.