The fact that TCEC games aren’t all draws suggests that computers aren’t perfect. Stockfish loses to Leela sometimes for example.
Tcec games are deliberately played from imbalanced opening positions. The draw rate would be much higher for the top participants if this wasn't forced. However, I agree that engines are not perfect. I have heard this claim many times before a new engine came along that showed just how beatable the state of the art engines still were at the time.