Totally agree on both points there, and with the maxxis minions FBF 4.8, there are actually 2 rows of huge cornering knobs to rely on, both with nice big channels giving plenty of space to bite the terrain. Having an extra row of channeled cornering knobs makes the tires feel like they are eating the trail. Also, the fbf knobs are huge and very stiff. The large, spaced out channels really allow for the corners of the knobs to bite and grab dirt and rocks....You're really just relying on one row of knobs. Do you think increasing the width (the amount of rubber not in contact with the ground) is really going to help when the bike is leaned over?
I suspect that for cornering grip in mtb tire tread design you need 1) the tread blocks of the cornering knobs to have sufficient size for stiffness and stability (aka tread block stiffness) and 2) a longitudinal channel (void space) big enough to allow the biting edge of the cornering knobs to exert enough force against the trail surface.
You can see here maxxis did a great job with the channeling on these tires.