Grogu is technically a relic of the era before the Galactic Empire having trained with past Jedi Masters and, since this appears to be a point in time when Grogu's memory is most clear, Luke may be able to learn something from Grogu in return.

Does Luke train Grogu?

At the end of season 2 of The Mandalorian, Grogu left with Luke Skywalker. ... When we last gazed upon The Child (a.k.a Grogu) in The Mandalorian season 2 finale, we saw him leave in the arms of Jedi Master Luke Skywalker to complete his training.

Why does Luke train Grogu?

The seeing stone on Tython has done its job: Grogu is now in the care of the galaxy's greatest Jedi, Luke Skywalker himself. ... It's during this quest that he finds the sacred texts Rey encounters in The Last Jedi, as well as some records belonging to the High Republic's foremost Jedi, Avar Kriss.