Honestly unless the temperature in your tank is lower (significantly) they aren't going to go into shock, and odds are the temp in your tank is higher, so that shouldn't be an issue. I do actually float store bought fish that have only been in the bag 30 mins or so, but the concept of squirt and dump with shipped fish is to get them into clean water asap, as the water they are in is nasty. There is no drip or floating because as I said, the temp in your tank is likely higher, and higher temps amplify the adverse affects of ammonia, which is probably present in a higher than normal concentration since they've been in the bag so long.
People are afraid of this method because they learned the old way of doing things. The old way didn't incorporate fish bought online lol.