Thanks for pointing the article out. Whilst trying to learn it is useful to take a step back and look at how you are learning.
The part I find most interesting concerns section 5.3 'Practicing the ability to look far ahead'. They conclude that '... depth of search should be seen as a consequence of acquiring a large knowledge base, which, through chunking of moves and creation of templates, leads to a more selective and efficient search.' I would interpret that as suggesting it is better to practice lots of shorter tactical puzzles quickly rather than longer more complex puzzles more slowly until you have developed a large enough personal knowledge base.

? Actually I disagree with one other point. The authors recommend sticking
? to a very narrow opening repertoire, and practicing not only the opening
? lines but also the typical middlegames and endgames that result from those
? opening choices. This, I believe, may be good for short term results, but
? could be detrimental to one's long term development as a chessplayer. At
? some point, an aspiring player ought to learn how to play with and against
? an Isolated Queen Pawn, conduct a minority attack, launch an h-pawn against
? a kingside fianchetto, maneuver against a hedgehog, etc. Which is to say,
? acquire a rich collection of chunks and templates, including the most
? important ones.

I agree that as a long term plan a broader opening repertoire may be required, but how many people get beyond the short term?.
I think it very much depends on your aspirations and your available time as to how you develop this repertoire (if at all). The approach of having a narrow opening repertoire and practicing the positions through to the endgame sounds a practical way to develop for most people. I am never going to be an IM or GM. I would like to improve and the way that this improvement is measured is by beating other people. If your choice of openings never has an IQP then learning how to play such positions won't be that helpful. I will never be a 'complete' chess player but that doesn't matter. As I improve (hopefully), I will develop a larger knowledge base and be able to add more chunks and templates.

The authors do suggest in their conclusion that to advance from Master to Grandmaster that the opening repertoire does need to be widened, but for other people it doesn't seem to important.

?They say that blindfold chess ability
? comes almost automatically once the player has acquired enough "chunks" and
? "templates" (=pattern recognition and deeper understanding); unless the
? player has reached that point, it is not efficient to practice it.

If this is the case then an ability to play blindfold could be a barometer of your ability or to phrase it in a more painful way - if you can't play blindfold you're not very good
?