True Seeing's text states:
For the duration, the creature has truesight, notices secret doors hidden by magic, and can see into the Ethereal Plane, all out to a range of 120 feet.
Here is the definition of truesight:
A monster with truesight can, out to a specific range, see in normal and magical darkness, see invisible creatures and objects, automatically detect visual illusions and succeed on saving throws against them, and perceive the original form of a shapechanger or a creature that is transformed by magic. Furthermore, the monster can see into the Ethereal Plane within the same range.
(Emphasis added in both cases). Since truesight already includes seeing into the Ethereal Plane within range, and the range for both truesight and seeing into the Etheral Plane from True Seeing is 120 feet, what function does that clause in the True Seeing spell have?