The gym where I train (Pure), has those same bars on all the cable machines. I use those same grips (a semi-supinated grip) because they're easier on my joints.
They hit both biceps and lats on me, similar to a close-grip pulldown. I'd say they're closer to a chinup, but without all the elbow stress from fully supinating your grip. Thumbless is fine, but some of the grips on the bars have loosened up a bit and twist under my hands, so I use a normal grip.