Does changing in Shanghai on my way to Hong Kong prevent me from having a 72 hour free transit visa?

I arrive in Beijing from Manchester, and 70 hours later I'm off to Hong Kong. This flight is via shanghai, because there don't appear to be any direct flights to Hong Kong, does this prevent me from having a 72 hour free transit in Beijing? In other words am I officially going to Hong Kong or am I going to shanghai and then going from Shanghai to Hong Kong.