Price fixing is when two or more land lords agree to not lower their prices beyond a certain point. There is no agreement here. I don't see how this is price fixing.
Search for "adherence to the agreed-upon Prices", "fix list price", and "Express delegation".
They argue that collusion through delegation counts as price fixing. They argue colluding to set list prices even when there isn't a price floor is price fixing. They argue that replacing the delegation with an algorithm is still price fixing. Most of their arguments are based on already settled cases.