3.1. It can also be said as constructed due to HZMB, which won't be reflected here. That's geography. 
3.2. Again, they merely shows you why you can't exactly use a three-way interchange's layout. Both Quarry Bay and Sai Ying Pun interchanges are mainly influced by turning radius,  reducing grade-separation span and distance (considering sloped ramp length as well), limited available land, etc. On the other hand, you could also say WHC and Connaught Rd W flyover route are continous along the median (the spit is simply to connect with the flyover, and still along the median), then it's the main route? 
4. You still didn't discuss why those `=primary` can't be `=motorway_link` 