Well... There is some theory behind the "Grab and plop" method for acclimatizing.
It's a commonly accepted practice at least in the discus world to "Acclimatize" fish that have been in shipping for longish periods of time. The theory being, once the bag is opened there are some radical changes in the water chemistry due to the sudden influx of oxygen. It is felt that the stress of the "Grab and plop" into a good environment, is better than to be left stewing in ones filth in radically changing conditions.
Now that said, they're talking Discus in bags for 12-36 hours... Not exactly Fish coming home from the pet store.
Personally I'm a lazy SOB and I've gotten accustomed to the grab n plop - but I still drip acclimatize any fish I feel are sensitive or are worth enough that I feel the urge to take care of
There ya have it grab n plop in a nutshell... I'll just shaddup about Saltwater fantasies; as some people apparently really like him.
Andy