Look I don't doubt the Su-57 is an excellent 5th gen fighter but what else is Bogdan going to say? That it's production rate lags the Chinese and even the Americans? He was mostly referring to kinematic performance for which Su-57 seems to place high emphasis on performance within certain speeds and aerodynamic preferences. Overall, you cannot cheat known physics and there will always be aircraft that perform better in certain ways. Some sure are better overall and Su-57 could be one of those which are just better overall but that remains to be seen. It sure is the best looking one IMO.
Can he speak to the all aspect stealthiness? avionics? electronic resilience? These certainly are more important performance measures. Not to mention the production rate and cost for which China is even surpassing US production rate for its own use F-35 if we add J-35 to the 5th gen inventory.
At this point, many China doubters will begin the usual internal dialogue of 'china can only do volume but not quality' ... to that, well I just have to sigh and smile at how untrue that is for plenty of production types. Certainly Russia is not quite at the same level overall, perhaps within some remaining niches, Russia is indeed top of the world but those are reducing.