I think the extra linkage creates a virtual pivot point, more complexity, but can allow the rear wheel to travel in a more vertical path. My 2004 Specialized Epic had something similar which provided a very good FS ride. Since then Specialzed has changed that design to be more like the single pivot designs we see from other manufacturers. The biggest issue I had with my 26" Epic was the low bottom bracket height, lots of pedal strikes and I needed to be really careful when gong over log piles. I know the Epic 29er improved the BB height but the new design removed the lower link which makes it more like an IP-036, just with a Brain Shock so it has the auto-lockout which can be debated as to how well it works.
The Fox CTD shock on my IP-036 works really well. Full open (D-mode) the suspension is very active and soaks up the bumps, in T-mode, shock compression from pedaling is minimal while still absorbing small-med bumps, in C-mode the shock is 90% locked out but still provides absorption of small bumps.
So in today's single pivot designs, the shock can do more of the work and can make up for the simpler, less tuned, suspension design.