If you think about it, this is a reveal that the show has been building towards for quite some time; we really should have been suspicious of Mari s Delicioustone breaking in the first place.
Yui is learning to be her own person rather than a carbon copy of her grandmother, as well as to see the shades of grey in the world, and those may well be the most valuable lessons she s picked up as the story heads into its finale.
Where Narcistoru resented people having good memories involving food, Secretoru seems to be motivated by a desire to gatekeep recipes – believing that only qualified people should be making them.