CX520/521 is the NRT rotation with long haul products most of the time. Seems that CX520/521 is now normally operated by 33K/33E, with the occasional 77G/77H...(whereas on like 504 and 450, you will 99% get a short haul configured aircraft...I wrote about this somewhere else) but given that the norm for CX short haul is to subject all routes to substitutions, not surprised that there's been changes here and there. However, I think that CX equipment swaps on regional routes have decreased significantly compared to the past.