That's the thing with dealer technicians. They follow a recipe - there's one guy at Klosters who has some nouse but I think the rest of them just follow the instructions provided.
When replacing the EGT sensor - which is a probe around in the exhaust manifold - there won't be any need to undo the EGR pipe on the intake side, the instructions won't say it's necessary and so they won't go anywhere near it.
For most situations, that's actually a GOOD thing. A large number of problems are fixed quickly and easily (and properly) by following Nissan's recipe. We see a greater proportion of "out of the ordinary" problems here, because ordinary ones are fixed so quickly there's no need to talk or complain about them (remembering that forums are magnets for complaints).
So we SEE a high proportion of those odd issues that aren't covered, but it doesn't mean that Nissan's "big picture" is unsatisfactory. All manufacturers would be like that these days - it guarantees consistency, and predictability.
And the dealers would have to make sure their techs are following the recipe - because if they don't, Nissan may NOT pay the bill (because Nissan needs that consistency).