That is correct.On the interesting points Taxiya raised about reaching supersonic speeds with only dry thrust. He is more or less correct except breaking the sound barrier imposes a dramatic increase in drag. This means the aerodynamics of the fighter comes into greater play. Since we don't know the specifics here and we can't eyeball it, it's impossible to say whether or not the flanker series can supercruise even if their engines are not stopping them from doing so.
If I may rephrase it. "it's impossible to say whether or not the flanker series can supercruise if their engines' thrust-to-weight ratio is above or below a certain value.