In truth, you are looking for a specific answer that does not exist. Simple as that. Here is a different take.
Loin back ribs/baby back ribs - traditional thickness, are separated along the seam of meat, between the loin and the thin layer of meat over the rib bones. This layer of meat is typically 1/4" to 1/2" over the highest part of the bone.
Loin back ribs/baby back ribs - extra thick, the seam is ignored and the ribs are separated with the loin strip being removed and the remaining meat left on the rib bones. These will be anywhere from 1/2" to 1-1/4" of meat over the bone.
Spare ribs, again, there is a natural seam, that separates the meat on the rib from the larger cut of meat above the bone. If separated at that seam, which is almost never the case, you end up with around 1/2 inch of meat over the bone. Most often it is cut closer to maximize meat and minimize ribs waste.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."