Is the prayer valid if a follower prays behind a Meccan resident who shortens the prayer in Arafah?

Primary text

If a man prays behind a Meccan resident who shortens the prayer in Arafah to two rak'ahs, and the follower then stands up after the Imam finishes and adds two more rak'ahs, the prayer is valid. This validity is because the Meccan resident shortens the prayer based on a permissible interpretation (ta'wil), thus validating the prayer of the one following him.