Yes, and no. The less unharmonic bass strings make a noticeable difference for the middle and high register too, when the dampers are lifted by the sustain peda

Yes, and no. The less unharmonic bass strings make a noticeable difference for the middle and high register too, when the dampers are lifted by the sustain pedal and the bass strings resonate with the higher ones. This "roominess" is also noticeable on the old long-neck lutes like the chitarrone, which had long bass strings for the same reason as this piano: avoiding wound strings (in their case, because those hadn't been invented yet)