That's how theses cases usually work. Antitrust claimants want to define the market as narrowly as possible for their own benefit. Defendants want to define it

That's how theses cases usually work. Antitrust claimants want to define the market as narrowly as possible for their own benefit. Defendants want to define it as wide as possible for the same reason. It's up to the court to figure out what the actual market is, and not what the (biased) parties want it to be.