I’ve dealt with this one for years, with some smug incapable professionals as well as high-self-opinioned amateurs saying the same thing.
That no good craftsman observes what the shavings from the plane look like. The response is this. “I look at the surface, it’s the only thing that counts”.
First, the easiest way to tell if you’ve set a double iron properly is to observe the shaving. If it worked by the action of the cap iron, it will take on a different quality – from somewhat irregular to thicker shavings actually going straight for their entire length or long sections. This is useful to see – it doesn’t guarantee no tearout, but it guarantees safe planing for the time being. Without this cue, you’re potentially headed into the weeds blowing past marks.
Second, fine tearout that ruins a finish planed surface or shows up only once you apply finish will show up as discontinuity or holes in thin finish shavings. This kind of thing is hard to see on the surface of bare wood, or judge if it’s just the structure of the wood (lack of density in grain) or if it’s actually fine tearout.
To tell beginners that nothing can be discerned from plane shavings is stupid, and when it’s paired with assertions of much professional accomplishment, the accomplishment and the planing are not linked.
This kind of stuff is just too bad, but as mentioned in the prior post, you can’t bulldoze water uphill.
What do most of these folks do? I’m sure they sand everything, and their use of planes is far more infrequent than they admit. Some of them I know from actually talking to them. With revisionist opinions about good plane setup that match nothing that they said prior to 2012, it’s a bit obnoxious.
You may be asking, what’s the big deal if you’re going to sand? Aside from giving terrible limiting advice to people combined with puffery, even if you are going to finish sand a surface, you will be able to do it far more quickly and to a final level if you are good at planing a clear surface. Perhaps in one linear grit.
Someone capable with planes will not rely solely on shavings, but they will discern an awful lot from them.
Of Making by Hand with Wood and Steel 
“I don’t care about shavings” is usually followed up with “but listen to the sound the plane makes, THIS IS IMPORTANT” under the same breath.
Seriously though, the advice to not pay attention is probably targeted at beginners that over optimize for a thin shaving. They try to push a tool way too far beyond and often don’t notice how they have to resharpen after just one shaving or how a blade leaves white marks after just one swipe. Meaning that maybe some degradation in the quality of cut should be traded for the time being for edge retention — finishing planing is way more than just a sharp tool, right? Most probably a beginner won’t be able to leave planed finish even of he would borrow sharpest planes somewhere, some sanding will be employed, so maybe don’t worry about sub-micron shavings just yet.
Otherwise shavings are just like dissipating heat on a BBQ: it’s not served to guests, but it’s an absolute tell tale how your meat will come off a grill. Some people choose to ignore it and go with something else, but for the rest of us it’s such an immediate factor
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