Ask the pool builder what happens to pools that run really high salt levels for their chlorine generator, and how is that salt okay but the salt from bleach isn't. His response is sure to be nonsensical and comical.
The main reason pool stores and builders advise against Clorox is because you don't buy it from them. Funny thing is, every pool service truck I see -- and there are a lot in SoCal -- has the orange and yellow HASA crates in the bed. They might use pucks to maintain FC during the week when they aren't around, but when they visit, they use 12.5% bleach to boost the FC!