I love this stuff (as can be seen from the
dungeon I contributed to this thread).
I like that James acknowledges that recent editions have lost the vocabulary for this stuff. I agree that this has led to it becoming an implicit part of the game known only to experienced DMs. This is not something that new DMs know to do. If you take away the name of something then it dies out of the game.
However I think when the discussion moves to specifics the quality is pretty mediocre and I wish someone else besides JW would write this section of the 5e DMG. I'm not sure that the subcategories of tricks is a useful schema. I don't see any important difference between obstacles, dungeon dressing and hidden things--put examples of each, but don't imply that there needs to be an even split between them among the tricks in a dungeon. Mysteries seem like a different type of thing, because they involve clues garnered from multiple encounters and generally the stakes are much less immediate. But they're fun so they should be discussed somewhere.
A couple of specific criticisms: JW says "traps whose sole purpose is to punish characters for not finding them (often with sudden meaningless death)"--no, the purpose is to make messing around with stuff in the dungeon more tense, which some people find enjoyable. Sudden death is not meaningless if the player has made an agreement with the other players that their character will be the doppelsoldner (first person to mess around with dubious-looking stuff in exchange for first choice/larger share of treasure).
"Teleporters, stairways at the end of sloping passages, rotating rooms, elevator rooms, distance distortion, and similar effects just confuse the players about their position in the dungeon. In practical terms, their primary effect is causing arguments between the players and the DM over the accuracy of the players’ map."--no, what's supposed to happen is that the PCs start moving through terrain they've already been in, or terrain that should be much farther away than it seems to be, and the players realize this from the description, which surprises them but makes them feel relieved and smart. The problem is that it's annoying to erase part of their map if they're doing it square by square with pencil and paper, but this is an issue with that particular mapping practice not with the whole idea of navigation as an enjoyable player-level challenge.
I don't think the game should tell players to map a dungeon square by square. Players should decide for themselves how they're going to avoid getting lost (take note of landmarks? make markings with that chalk that's on the equipment list for some reason? make a simple line map?).