Well, I can understand it if you look at the first two sentences in isolation. Taken in context with his other examples I tend to agree:
>>An encounter with two guards at the city gate isn’t fun. Tell the players they get through the gate without much trouble and move on to the fun. Niggling details of food supplies and encumbrance usually aren’t fun, so don’t sweat them, and let the players get to the adventure and on to the fun. Long treks through endless corridors in the ancient dwarven stronghold beneath the mountains aren’t fun. Move the PCs quickly from encounter to encounter, and on to the fun! <<
The problem is simply that a guard encounter is not a very good example of something that should be skipped (always). Isn't it telling that it's called an encounter?
In my experience players are usually quite grateful for the change of pace that encounters with mundane npcs bring about. Dealing with city guards, merchants, innkeepers, farmers or urchins can be fun to roleplay even if (or precisely because) there's nothing important at stake.
It's also an excellent means to provide some setting background and feedback regarding the pcs' adventurous exploits.
Of course you can overdo it and an entire session spent going shopping and talking about the weather will be boring.
The rest of the examples are better, imho. Taken with a pinch of salt, the advice is good.