Need help in understanding flip flop
No, your analysis is NOT true. Even when Q' &rarr; A goes high, since the S' input is still low, the Q output remains high.

And despite the comment by Ignacio Vazquez-Abrams, the both-inputs-low condition (and both outputs high) is NOT an "unstable state" in itself, but the state that the circuit ends up in depends on the order in which the inputs go high. If they go high "simultaneously" (not really possible in practice), it's impossible to predict the output state, and the outputs may even become metastable for a period of time.