We saw from the Somniel video and today's Twitter post that you can still talk to others between maps, have tea time with different characters, workout with them, dress them up etc..so I think there's actually plenty of social sim mechanics in game.
Which makes me think they're hinting at the lack of S supports which is arguably the most 'important' social mechanic for FE fans that play for the social sim aspect. Which I guess is also why they said those fans may be disappointed. It also matches with the lack of romance tag in the Japanese rating for the game.
If it's true, it's a very strange decision to make.