As said, all airlines overbook. Popular airlines and routes are often worse.

I was on many longhaul CX flights that were overbooked. There were several that even J were booked. I was told that some J passengers had to travel on Y.

When I checked in at SFO, CX did tell the passengers during check-in so that they can be offered compensation (varied) if they chose to give up their seat. I heard them asking nearly everyone - except me, but neither could I get an op-up.