I always thought that the term "price fixing" referred to two or more competitors agreeing to sell their rooms at a certain price without undercutting each other.
I didn't think that simply selling their own rooms at a fixed price would be called "price fixing".
HTB.
The problem is that they have been accused of preventing agents from selling them at a lower price, and taken action to prevent it. In other words, they have taken action to hold the price up. In this case they have been accused of undertaking the action and the two other respondants in the case; Expedia and Booking.com, who have been accused of going along with it, creating the collusion.