Rick,
I have a Woods HB-72 and it has an ID plate pinned to the left side of the top link support plate. Mine says its mass is 621kg. I know it doesn't weigh 1366 lbs so I placed a call to Woods. I was told that the 621 was pounds and not kgs less any accessories, including the shanks.
Their specs for the HB-72 says it weighs 660 lbs, so if I weighed the shanks, pins and clips, they should total 39 lbs, which added to the stated 621 lbs equals 660 lbs. Sounds good to me. Check and see what your ID plate says and let me know. I agree with you, the HB models should weigh more than the GB models, size for size.
Kub