First, the idea that 2 lbs/week is the maximum amount of weight/fat loss that should be achieved has been around for years but nobody seems to know where it comes from. Certainly there’s no physiological reason for this to be a maximum and much larger rates of true weight/fat loss can be achieved with extreme deficits.
Anyone who has watched The Biggest Loser knows this to be true and even without that level of asininity, very large folks following a protein-sparing modified fast as per my Rapid Fat Loss Handbook have been measured at 1/2-2/3 pounds of fat loss PER DAY. Which is 3.5+ pounds of fat per week. Clearly 2 lbs/week is a bogus value in a physiological sense.