Right. I don't think anyone's claiming that Pathfinder overall sold more than 4e, only that it did for a period of about 2-3 years when Wizards had basically shelved 4e anyway. For one thing, I would expect that a significant portion of Pathfinder customers had at one point bought at least the 4e core rules (and found them wanting).In the linked Twitter thread, Owen Stephens said that he and Chris Sims had both seen the internal sales numbers for both Pathfinder and 4E, and that nobody who had would disagree that 4E sold better. I don't got a dog in the hunt (barely played 4E, never touched Pathfinder), but the insiders who had access to the real numbers on both sides seem to be in agreement.
Also, while 4e's numbers would get a boost from mass market sales, Paizo sells a lot via their own web site. Probably not as much as WOTC does via toy stores and the like, but nothing to sneeze at either.