Think at it this way: if you are at home expecting some friend to have dinner there in the evening, you'll be glad to have them arrive no matter when; any pre-scheduled time would be arbitrary, so letting them arrive whenever it's convenient is good for them and doesn't have any drawback for you. In that situation, it would be incredibly rude on your part to yell at them because you previously agreed that they'd be there at 7:30 but they arrived at 7:54 instead; I don't know about you, but that would be unthinkable here. (Of course if they arrived at 23:00 that would register as "not showing" during the evening, but that's beyond being late).
That kind of lax schedule shouldn't inconvenience you, because you're otherwise comfortable at home arranging all the details; and it can bring benefits for them that couldn't happen otherwise - they may want to stay fifteen more minutes having a coffee at a bistro, watching the sunset, for example; it would be a loss having to rush to your meeting merely because they know you're hardheaded about meeting timelines.
Of course that can be seen as "not efficient" in the "cram-as-much-things-to-do-as-you-can" sense of efficiency, but as explained in the article, that's not seen as a value on itself. And, if you find that having your friends enjoy the smell of a rose is less important than them arriving at an exact time, it speaks very poorly of you and your ability to find other things to do when unpredictable events happen.