They are misusing the term for what they are doing. What they created is a program that price discriminates. Price discrimination based on purchasing power parity is a much more accurate description of what they are doing rather than just just purchasing power parity. Of course, it is possible that the author knows this, and is just avoiding using the term 'price discrimination' since it sounds bad outside of the academic context.

They aren't necessarily leaving money on the table, although an argument can be made that purchasing power parity isn't the best mechanism for profit maximizing using price discrimination.

The point the OP is trying to make is that this isn't some revolutionary new tactic that the author invented by understanding PPP on a deeper level than anyone else. This is a concept learned in intro to economics. And one that is used by a lot of online service providers already.