It opens for "2nd teams" blocking points from other manus, so we get fewer situations where a driver finishes 30 mins behind on 30th place but still scores manu points for 5-6th place.

However, this:

5.3.5 Cannot nominate a driver who has been nominated to score
points in the corresponding Manufacturer Team in the same
season.


Makes it very problematic for Hyundai (and easy for Toyota with Katsuta). Hyundai would want to use Mikkelsen or Breen in the main team for Sweden/Finland/GB, this way they can't without removing the blocking option on other rallies.