It's a realistic touch that you can't just rewrite a person's entire personality, which was basically what Heronia tried to do. Cecil, as he is now, does understand (others) emotions far better, but still does most of what he does because he knows it would make Bertia sad.
Technically, Bertia was doing that from the start, trying to make Cecil interested in various things by spoiling the "story", which made him experience many emotions he didn't felt.
Heronia met Cecil when he was around 14to-15yo, compared to Berita when he was 10yo, in the original timeline (game) it was too late for Cecil to grow naturally so light spirit (drugs lol) had to be used otherwise Cecil wouldn't follow her as he was already too broken.
Cecil developed an obsession in each route, but now is "just" obsessed over Bertia, yandare level obsessed. Already controlling what she does, where she goes, who she meets and thanks to the Zento mark knows where she is all the time... yikes...
Heronia might be sent to monastery far away where she most likely die, as they mentioned, but at least she didn't end up with a sociopathic yandare...