Well an appreciation of and willingness to play out slightly dry seeming technical positions is certainly very useful in practice so probably very sane advice. The hope would presumably be to round out your style and get you enjoying playing that sort of position rather than trying to force tactics.

This is quite distinct from improving young people etc - you can't play technical chess (and especially endgames) without at least decent calculation. And fairly open games are the way to get that.

The problem is of course that improvement by doing things which aren't inherently fun is very hard to without very strong motivation.

Which isn't something many people have After all obsessing over improving at chess is objectively a marginally odd thing to be doing!

Interesting discussion. After looking at the repertoire, my opinion is: it looks like a good repertoire for masters. I'm not so sure about the White side of it being a good choice below master level, but the Black side of it could well be.

Why?

I think sub-master players (I'm in this category) should open with 1.e4, and strive to play aggressive chess. 

I have three main reasons for this opinion.

Firstly, 1.e4 seems to lead to central pawn formations that are considerably less diverse than those arising from the closed games. 

Secondly, 1.e4 embodies logical principles of rapid development and central control, hopefully in order to build an attack. Playing e4 practically forces one to learn the principles of attack, principles which are very valuable because...

Thirdly, sub-master players are apt to let themselves get flustered under aggressive attacking pressure. Whereas a master under pressure cooly keeps their head and plays active defence, a sub-master is often cowed by an impending attack and adopts a passive, overly defensive attitude, missing opportunties to counter-attack and play actively. Therefore even slightly unsound attacks can be very successful against amateurs. And of course, 1.e4 offers a range of interesting attacking systems for the White player.

A minor reason is that 1.e4 is a salutary lesson in how damn hard it is to gain an advantage against 1...e5! The Sicilian, the French, the Caro - these offer White the opportunity to play interesting, attacking lines. But 1...e5! Well, what to do? The answer - adopt a more strategic system such as the slow Giuoco, or the Spanish. And this, of course, is good training for... the closed openings! 1.e4 can become a 'strategy university' in an effort to meet 1...e5. Perhaps, when Master level is attained, our erstwhile 1.e4 player can switch to the more positional worlds of the closed openings, fully schooled in aggressive play, and soundly introduced to positional concepts, through experience with the king pawn opening.

Now, as to the Black half of the repertoire, this looks quite suitable for amateurs to me, mainly because the defences chosen are respectable, active, and don't give up large amounts of space. Of course, the price is theory - a whole ton of it. Okay, but over time, if you choose a good defence and stick with it, it can last your whole chess career and thus one can accumulate the theory slowly.

I don't know if I'll swap to the Black repertoire just yet - I've got to work on my White e4 repertoire first - but I may well swap to the Breyer and Grunfeld in the future.