Planning to skip a leg between PEK-PVG having flown in from UK and just wanted to clarify that the above scenario would only apply to a INT-CN-INT itinerary, is that correct? I would have to clear immigration at PEK anyway for a domestic connection if I was planning to take it, right?

I'm a skiplagging virgin - is it courteous to inform the airline you cant make the flight (for some BS reason) or do you just vanish into the ether....