It doesnt matter where the lift capacity is measured, just compare apples to apples. That may be JD lift at the pins vs kubota at the pins, or JD at 500mm forward vs kubota at 500mm forward. Just dont compare Pins of one tractor to 500mm forward of another and think the one measured at 500mm is weak.
I always look at lift to max height. Another spec to look at is the breakout force. It is a combination of lift and curl force that represents the ability to "breakout" of a pile of dirt or whatever. But again it can be measured at the pins or 500mm forward.
Just as an example kubota and JD are good about giving specs at both 500mm and at the pins. Whereas kioti and Mahindra like to give only the spec at the pins, cause it is higher there and looks better. Now I'm not bashing kioti or Mahindra cause they make good tractors, I'm just stating facts and you need to compare apples to apples.
Measuring at the pins is a good point for comparison but in no way is the actual lift capacity of the loader, as the bucket is way out in front of the pins. Thus the 500mm measurement is actually about how much you can lift in the bucket.