Front subframe sitting on bump stop ?
This isn’t actually true. What is not true? I understand that there are different optimal settings for radial vs bias ply tires, but this person is running his suspension at the bottom of the available travel and actually on the bump stops. That is not good for several reasons, which don't involve the difference between the settings for radials versus bias ply tire settings.
Using a 2 inch drop spindle, and adjusting the torsion bars up so it is closer to the middle of the available travel, is going to allow for be much better ride quality among other benefits than lowering the suspension onto the lower bump stop.
You mention that the geometry is altered with drop spindles due to the movement of the spindle location in relation to the ball joint positioning. I learned long ago that you are very knowledgeable in regard to suspension tech, and have enjoyed many of your posts but, I'm still convinced a drop spindle is the way to go if a person wants such a dramatic lowering of the front of the vehicle. I personally don't like my cars that low, but to each his own.
Are you saying that this isn't true? Please elaborate.