How accurate is flightstats.com?
 

CX 888 (CX) Cathay Pacific Airways HKG 12:30 AM YVR 9:25 PM for June 25th. Flightstats.com shows 2 in First, 8 in Biz, and 9 in Coach. I just tried to buy it online on the CX website and shows Biz all sold out with only a few seats left in Coach....

Is Flightstats.com usually this unreliable?

for me it seems very unreliable. flights supposed to be full were light and vv

I do not know for flightsats, but expertFlyer shows availability for US point of sale. Iassume flightstats does the same. Indeed F2 C8. EF is very reliable (everyone has the same info), but it only applies to US POS. However, full fare tend to be identical whatever POS.
Furthermore, CX also shows plentu of availability availability in Biz on CX888 25 June. Maybe you typed a wrong date,