What a load of crap. Pocock destroys this strategy. Just refer to the RWC for this.
There is really no reason why a pack of 7 can't play the way you describe and have only ONE player prioritising fetching and slowing the ball down. A good seven will still pick his moments - so its not like they are losing anything.
It isn't the way is being played. Pocock is the variant from the norm, most 7s these days are all-rounders, they can all do it, they are now just expected to do much, much more and the fetching is more opportunistic across the whole side.