I suspect this was actually a legal routing for an AS award on CX, because AS publishes an award chart for continental US to Africa on CX, JFK-HKG counts as a TPAC flight, and you can add flights on CX or AS domestically, even if the routing doesn't make sense 100%. You have to take award space where you can find it.
It was 4 CX flights and each segment was international. CX doesn't have US domestic flights. AS published a specific award chart for CX YVR-JFK as a standalone on the 5th Freedom flight. It was separate from the Canada/Contiguous United States & Alaska - Africa charts. CX already flies YVR-HKG and it was 'generally' not combinable to fly YVR-JFK-HKG. Otherwise, if you were on the West Coast and wanted to get back to JFK you could hop up to YVR, fly to JFK in CX F and then continue onto Africa in F/J up to a year later on the same award utilizing the free stopover, all for 70K AS miles. Again, the route, after 26 years, is defunct.
Back to interline baggage: especially interlining to another domestic carrier, AA is motivated to collect its own baggage fee, or at least motivate you to book potentially everything on one, potentially expensive ticket. It would be nice if AA made its domestic fares combinable with AS fares for exactly this reason.
All that should change when AS joins OW next year.
James