So the advice is to use water that has *just* boiled (do we wait for a minute or not?) and to brew until the leaves open. Hopefully they open quickly, otherwise we'll get some bitter tones with the flavour. Or maybe my oolong isn't that great.
This will depend yes, on the quality of the tea, but also on the type of kettle you're using, and the brewing vessel. For a long time, I thought that "boiling is boiling", but different types of kettles retain heat very differently. A metal electric kettle, even when you don't use the auto-shutoff feature, will, in my experience, give different results 10-30 seconds after taking off the heat compared to a glass kettle boiled on stovetop or open flame, which will give different results from a large capacity, heavy earthenware / stoneware kettle. Slow, thin, high pour into thin porcelain will also change the results compared to direct, heavy pour into a thick clay teapot.
For the rinse only, I'd definitely try water that's at more or less a full rolling boil (but not super-boiling) for a quick pour, wait a little and don't reboil before the first infusion after the rinse, then see if the results get too vegetal or bitter for you. If they are, you can try backing off next time.
It also depends what type of flavors you want to bring out. With a lot of gaoshan tea, and greener oolongs in general, I find that I can often get the flavors I like (less vegetal, more fruity) with just slightly off-boil water, but it's a fine line to get enough heat but not too much. Some people are more interested in texture / thickness, and don't mind the vegetal flavor; these people may use hotter water.