Lewis,
There are no rules for it. I am a poker dealer instructor and I have been teaching dealers for over thirty years and I think that there should be. I have seen dealers turn the flop one card at a time. I don't like it but, they can do whatever they want if it is accepted. I would like to see a standardized set of rules and procedures for dealers as well as players. Just my observation. I will say this, just because you see it on television, or at a tournament or in a casino or, on the internet, that doesn't necessarily make it right. There are a few books on the market for dealers that are pretty good, but how do you get everyone "on the same page?" It is very difficult. I applaud the TDA for trying to standardize a set of rules that everyone could use, but as soon as people disagree, they will continue to do it the way they want, unfortunately.
Not a rule, just my observation.
Nick C