How do contractors deal with an unleveled Kitchen floor?

Hi everyone. I'm in the process of remodeling my first floor kitchen that is built as a back extension to the house by previous owner. My contractor ripped the vinyl flooring until the last subfloor. The subfloor is leveled to the livingroom and hallway entrances but it's sinking towards the center of the kitchen.which he used a self leveling underlayment with some cement boards in the center to bring it up a little. While I want to install a wood base flooring like LVP, he is adament in putting tiles because he say it will last longer. But my issue is that if he installs tiles then the kitchen floor will be raised about three quarters of an inch above the livingroom and hallway floor. Should my contractor be making an effort to remove the subfloor and lower the level with new plywood sheets so that it will leave enough depth to install the tiles so the it it leveled with the livingrrom entrance?