The two recorders stopped because of lack of power, not because of other damage.
I didn't write it proved it, only mentioned it is even more unlikely. This is because the recorders didn't record impact or other noises/data associated with shelling. It would mean that the first hit severed the recorders.
From other accidents (silkair 1997), we know that the CVR keeps recording about 250 msecond after power is severed (yes different CVR, but lets assume not different in this aspect), and some impact noise could have been recorded, even if power was severed at first hit.