The actual bearing housing around the tube ( that rotates for horizontal motion ) is no bigger than my old Zeta tonearm which has a similar layout. The Zeta effective mass is only 14g - so as you point out the apparent bulkiness around the pivot point gives no indication of the effective mass.
However the lack of specifications on either their website or reviews is an issue for me. Two of my favourite cartridges are medium compliance and will not work optimally in a high mass arm. I would not buy the arm unless they can tell me the effective mass.