After their engagement, he didn't get particularly close to Fang Rushuang. Forget touching her, there wasn't any kind of unnecessary physical contact at all. At most, he was just a bit friendlier and gentler with her in the office. There wasn't even a need to pick her up or drop her off since he was busy, he never asked her out, either.
The only change was—since he was engaged to Fang Rushuang—he didn't need to keep the company of other women for appearances anymore.
So, from an outsider's perspective, he showed respect towards Fang Rushuang—it was definitely not something he would do for other girls. Moreover, there were no more successive series of girlfriends. Fang Rushuang had chased him for three to four years and she was quite pleased with the way things were now. This at least demonstrated that Qin Zhiyou was serious about having a future with her.