The trumpet, french horn, tuba, and euphonium also rely on the tuning slide to control pitch, so that's not an accurate statement.
Indeed, a trumpet has one slide for tuning only and two more slides that are used while playing, so it's not even technically correct.
Do you mainly control pitch with the tuning slide or the valves on those instruments? I think you mainly control pitch with the valves and only supplement with a tuning slide for certain notes, depending on the instrument, and therefore the statement is accurate.