In your own view, does a fighter have to move up to heavier and heavier weight classes to be considered a great p4p fighter? Please explain the reasoning behind whatever answer you give.
Not necessarily. "Pound for Pound" greatest simply means that the selected fighter is the best boxer fighting. Granted, there is almost never one division that is thoroughly stacked deep enough that a boxer could lay claim to the P4P crown by clearing it. If there was a hypothetical middleweight division of Monzon, Hagler, Hearns, Hopkins, Fitz, RJJ, and Toney, and Monzon beat them all, then I'd consider him the P4P best. He doesn't need to vacate the division and search for scalps at a higher weight. The problem is that today there are really only a few extremely good/ATG fighters in each individual weight class. A fighter needs to clear multiple weight classes and many great/ATG fighters to stake a serious claim to the P4P crown, unless they clear a STACKED division (as stated above). In a case like this, the multiple weight class domination thing becomes a sort of tiebreaker. It's hard to judge individual resumes in individual weightclasses, in this day and age.