Well, I am already almost blind, so I don't use blinders, but instead glasses! 😁

I have no interest in guessing who defends what position or why they do it. I am interested in the betterment of the game and ecosystem. I see this proposal as a move in that direction by incentivizing more development in more areas.

You surmise that this threatens PM's competition, but have you considered that it would actually encourage others to compete with PM's listing interface?

I believe more competition is better for everyone. If a 3rd party marketplace is only used by people because it offers cashback, but is in every other way inferior to another 3rd party site, why should they be allowed to earn market fees for little or no work?
Shouldn't they be incentivized to improve and build more and better tools?