[Someone1234]

F-22 isn't a "stealth fighter" it is a fighter with stealth features to reduce its radar cross-section and by extension reduce the distance at which it can be detected.

F-117 and B-2 were attempts at making an actual stealth fighter (completely radar neutral) and even an F-117 was shot down by a Isayev S-125 in 1999. I'd imagine China has at least access to that level of technology.

There's also work on infrared detection and optical detection which weren't possible way-back-when, but with access it inexpensive compute power, might now be a viable way to track even a radar neutral aircraft.

All I am saying it, I believe them, but I am also unsurprised. Against a nation like China I wouldn't even trust the B-2 Spirit to remain immune from interceptors, let alone the F-22, and frankly if China and the US ever went to war drones and missiles would likely play a greater role than manned fighters.