In fact that's not correct and there are many places where a readback of a readback is commonplace. Indians, for example, for some cultural reason fly around needing the readback readback and ending their own readbacks with, "...confirm?"
I wouldn't go using the JFK/China exchange as an example of anything other than disgraceful controlling. So bad the poster has taken it down from youtube I believe. The same New Yorker would be hopelessly lost in Peking, wandering the streets asking for a hot dog and not knowing a single word of the local lingo, unlike the Chinaman he blasted on the radio.
Sadly, the Canucks are indistinguishable from the yanks, I'm afraid. Comes from being on the same airwaves presumably. Bad RT and folksy, yokel terminology spreads on VHF exactly like a virus and you now have Indians "checkin' in, on handover" and pilots from the 'stans with their squawk codes "...comin' down" or in some cases even "... comin' up." Even ATC catch it with middle-east controllers requesting pilots to "...say your altitude" instead of "report." Every second pilot around the world is beginning a readback with, "...Okay understand."
The Brits aren't much better with "fully" this and that which has crept in. You're either ready or not. Established or not.
It's not hard; stop making excuses. There's a book, just read it.