PERSONA 5 Spoilers Follows:

Yeah, maybe they grabbed the description from variety. I just saw an article in anime news network saying that Variety messed up.

I think you got it wrong. From the Japanese trailer the plot is about the sister called Mirai coming from the future and meeting the boy.Not him meeting his mother in the past. Mirai = Future and is also apparently the name of his sister.That’s why the movie is named Mirai no Mirai (Mirai from the future).