I can confirm that HUCA works. First agent I spoke to (on WhatsApp) incorrectly told me it was not possible to split the PNR for a partner award ticket, and the entire ticket would need to be cancelled if I wanted to cancel the ticket for one passenger on the reservation.

I called the USA number and the agent I spoke to (located in HK) was able to handle it effortlessly. They even called me back when the call dropped halfway through.