This is nothing new. Of the ton of transpacific sectors I have done with CX over the years (YYZ/YVR/SFO/LAX), the bulk majority of them do not have Mandarin announcements. Ground staff at YYZ, YVR and SFO also use Cantonese during pre-boarding/boarding. But the LAX ground crews seldom use them based on my experiences departing from there.

I have never flown the JFK flights before so I can't comment there.