Sorry to revive this old Thread, but I recently received and Email from Western Powders on this subject. Thought you might be interested in their response.
BTW, the link in the OP (1) is broken. Maybe they removed it due to error?
My Question,
With all things being equal, Case, powder, powder charge, primer, OAL and bullet dimensions,
Which type of bullet generates more pressure/velocity?
Their Answer,
Jacketed bullets will create a higher pressure, because the copper jacket is harder to conform and push down the barrel compared to a lead bullet.
Go Figure?