Hao didnt train with the rest of the yuehuaz until they were all grouped together for boys planet but the show was delayed for like a year no? If I assume, then that's the time they all spoke with hao. They relied on hao during BP because he was like the leader of the bunch, I think they really started getting to know each other after debut. Yujin and gyuvin surprising get along with hao and hariboz even said themselves that they cant hangout together alone because their tastes are vastly different but I do think they have to be very comfortable to hold hands unprompted since ricky seems to dislike skinship and they dont look awkward