I think what the author meant to express is that the situation is symmetrical, even if one of the antennas is "better" (eg larger, or located higher up). So, author probably meant: "The bidirectional connection is symmetrical. It doesn’t matter (in terms of symmetry) if the AP has a better antenna or is located higher up".
So, even if the antenna on one side is "better" in some way, it affects both directions the same, and as such it still makes sense to use the same transmit power from both ends.
I think what the author meant to express is that the situation is symmetrical, even if one of the antennas is "better" (eg larger, or located higher up). So, author probably meant: "The bidirectional connection is symmetrical. It doesn’t matter (in terms of symmetry) if the AP has a better antenna or is located higher up".
So, even if the antenna on one side is "better" in some way, it affects both directions the same, and as such it still makes sense to use the same transmit power from both ends.