I'm not a fan of these key clusters, because of accidental key presses. Backspace is a destructive function.
Moreover, key placement *inside* the key section makes it more difficult to use while editing with the nav cluster (unless you're using a 60% keyboard with no nav cluster).
The whole debate would be over, if more vendors adopted split spacebars. That actually leads me to another idea: the ISO/IEC 9995 standard permits backspace on the bottom row. It could be a palm key in the corner…