There are no simple one sentence answers about grounding. It's not that simple and takes many years of practical experience to know what you are doing.
Entire books are written about the subject. I don't say much to anyone who asks about it (here) because I'm not offering a course on it. There is a lot of wisdom needed and every year digital circuitry goes up in speed.
The AD article looks at a few specific cases, gives orders on what to do... I don't agree with all of it but at least some equivalent circuits are presented. He ignores transmission line effects which I think is a mistake. I say 'proof is in the pudding' - look at Analog Devices eval boards, how they do the PCB layout. Not that they are always well done but apparently they achieve the IC's specifications. You'll soon see lately the approach is just to use more PCB layers and panic ground everything.
Because there is a disconnect between the PCB layout person and the IC engineering team and PCB layout is always a last minute rush at the end of that kind of project, it is not always done the best. When it fails EMC then people pay attention lol. But AD rarely makes product designs that far, so how can their people even know their approach is bad?