Yes the examples do matter because they don't support the function you are giving them.I'm not talking about making up new mechanics. In my example, the purpose of specifying "narrow passages" was so the Goblins could physically block the PCs. But there are plenty of other possible examples. In a town, for example those 8 Goblins might fan out with lit torches to ignite the thatched roofs of the nearby buildings. Sure, killing them all might only take 2-3 rounds, but it forces the PCs to choose between stopping and taking that time (plus any time necessary for firefighting) or letting the town burn.
In any case, the individual examples aren't terribly important. My point is that monsters can threaten the PCs' goals long after they stop being a lethal threat in combat. Many of the roles for monsters in previous editions didn't depend on being a lethal threat to the PCs, so those roles are still possible even with a reduced threat level.
no those goblins in a narrow hallway really don't. They either get nova'd down instantly to get them out of the way or it's an "epic" slog. The narrow hallway & 8 goblins against a high level party changes things too... fireball/lightning bolt/etc & go. You don't have the barbarian trying to charging/leaping power attack past the golem's dr or the high ac types cowering at range from the incorporeal creature while the dex types now up front are trying to keep it contained but are not too thrilled about the four skeletons up the hall... instead you have a whole bunch of monsters to wade over till the blood is ankle deep.