Is this true, have others experiences SP on PC for business credit cards from Amex?
I see no reason that should not be true. The true limitations on it are only being able to PC to other cards within the family. So those cards would be the core cards (Green, Gold, Platinum and Centurion) and Delta (Gold, Platinum, Reserve). Maybe the Amazon cards is included in this but not sure. You can change from Green to Platinum for instance but not Green to Delta Platinum for example.
Why would they do a SP for a PC? You're not applying for the card, just changing it to something else.