You forget that the setting they were asked to do this in, which was at Farnborough. Which is a tradeshow. Which is NOT an arena where you want to be proven to be inferior in any contest between aircraft.
The Su-35's manouverability is good, yes. But it is by NO means invincible, just as the F22, F35, Eurofighter or any other type of aircraft that flies the sky. Hell, even a MiG-21 can get a guns-only kill on an F22 if the F22-pilot quacks up. Which, in case you didn't know, humans are quite prone to doing.
One bad call can and will end your life in a fight, even if you're in an aircraft that should be superior in every measurable parameter.