A Seller would not have to say "feedback will only be left when positive feedback is received"

All the seller is doing is let the buyer know they have automated feedback set up and so if the buyer, for some obscure reason, wants feedback they will have to leave it first.

As a seller cannot give a buyer anything but pos feedback and the automated system does not come into play unless a pos it left why would you not buy from somebody who may be an excellent seller just because they want to keep you well informed?