1. First of all, you should check that Route 3  actually continues to San Tin Hwy, not ending at the interchange. TMCLK terminates at the three-way interchange, not favoring one direction; and it can even be argued Tsing Long Rd is the through route, as that's TMCLKL Southern Connection. I'm also talking about all the `=primary` , which can be `=motorway_link` . 
3. I don't understand that argument. That seems to be consider whether it's a  `*_link` , not the classification. 