It's not irrelevant when you realize that if your bike isn't good enough on the brakes because your chassis geometry and weight distribution doesn't allow for a heat build up fast enough to insure good grip, or at turnability or acceleration, the only way to recover it is to change this geometry and weight transfer, which is what Yamaha have done with the 2014 M1.
On top of which, last year partials demonstrated that Marquez was faster nearly everywhere bar the fastest curves, i don't think at Yamaha Racing they dare betting on his inexperience to manage tyres (as last year not before Assen) and race, or not being able to translate partial times, best race laps and poles into wins.
Point being, the limit on a bike is not that of the (rear) tyre but passed that.
I can enumerate the advantages of being able to slide a bike of this power and weight (from comments made by 500 champs AND personal experience):
First you can steer the bike in and out of a corner, and brake harder, then you can put the power down faster and earlier, therefore accelerate faster, then one other issue Yamaha had last season; tyre life-span, a tyre that slides on a patch away from its edge (you don't need as much lean angle to make the turn than with corner speed only) will last longer than when it is loaded at the edge for a longer period of time and abrasion is lower as well, Marquez won on a harder tyre than Rossi at Losail, that's one of the reason, less weight on the rear wheel.
A turn is roughly divided in to 3 section, braking area, turn-in/apex, and acceleration, the only reason 250/350 pilots favoured corner speed was the lack of power.
You learn corner speed from 125 cc and even 50 cc at the time, other than that there is no advantage to be gained over a full lap apart of very fast tracks where braking is not so important such as Assen, where Spies and Rossi won on "Lorenzo's" M1.
Using corner speed, that's only one area where to gain time instead of two, it's all about compromised but one is loosing less than the other and is a more difficult skill to master.
Progresses with the tyres are valid for everyone and the equation remains the same, Lorenzo age when Roberts was saying that his style was troublesome when the grip was low is totally irrelevant, Massimo Meregalli - Yamaha Factory Racing Team Director said EXACTLY the same for the SAME reasons after 2014 Sepang2 tests, lack of grip at the edge of the tyre, which is the 250/350 style problem, that's the relevance of Robert's comments.