debunix: yes that's pretty much what I was trying to get at and apologies for not being clearer in my initial question. As you say:
why choose one method over the other?
I think it's fair to ask the question. If the reason someone's doing high-leaf low-water for pu'er is because "that's what everyone else is doing" fine, no harm in that. But as MarshalN points out, it's only very recently that people started doing it and one aspect of the process appears to be connected with the marketing techniques of a large company.
Someone might say "well it tastes better that way" but I don't see the harm in trying to ask why: you can find billions of examples of people conning their tastebuds, taste-experience is extremely easily influenced by what you think "ought to" happen. Look at wine: experienced professional tasters are always getting persuaded to prefer the expensive wine to the cheap one, even if the labels of the two bottles have been secretly switched beforehand and they're actually singing the praises of the cheapo bottle. Or they'll even assume that they're drinking a red wine when it's a regular white with food dye, that's how much external impressions affect our sense of taste.
Now, if someone likes drinking pu'er the way that oolong has been traditionally drunk in the south "because of the centuries-old traditions of ancient mysterious exotic Chinese culture", well, that's bogus, as is saying "well that's how all the people on the English internets are doing it" ... and I don't think it's wrong to try to deploy a bit of thinking and drinking to working out if there are good reasons to go for the oolong-style leaf/water variables when drinking pu'er.gingkoseto
: the idea that different flavours take different amounts of time to emerge from the leaf and by shortening the brew-time you avoid allowing the longer-time ones to get into the water could indeed explain everything! Definitely something to think about. People sometimes make the final brew of a good pu'er by steeping it overnight and I've never got any bitter taste by doing that but I've not heard people doing the same with oolong: maybe that explains the difference I've found between brewing pu'ers and oolongs.
Finally: I agree that experience is crucial but I don't believe most people really rely on it from scratch. I mean, I didn't try one brew of pu'er with water at 10 degrees C, one at 20, one at 30 and so on all way up to 100 before repeating the process several times and finally deciding that boiling water worked best. We inevitably end up trusting what we're told before later (ideally) going back and questioning that early advice. Which is where my initial question was coming from.