It did happen, sort of.
After a few seconds of standing in the pool of unrefined stone he began to transmute rapidly and far neyond his previous skill.
you also have to consider that according to episodes 11 and 12 ANY exposure to the red water is extreemly dangerous to ones health. For Ed to have stayed alive after that much exposure was truely proof of how he was absorbing the alchemic energy and becomeing a stronger alchemist than before
Death is, as they say, the high cost of living.