In this age of inexpensive automation where I can buy for under $500 a processor of equal capacity to one that 30 years ago cost $50,000, it seems like it would work well to have an annunciation of major state changes - "GEAR UP," FLAPS 30," "FEATHER 1, FEATHER 2." Feeding back through someone who has made an error is feeding back through someone who already failed to notice they made an error. This would either enhance or remove the need for either pilot to repeat back what they were told and would give both feedback as to whether the expected action was selected so there need not be increased competition for hearing other communications. This might have been enough to avoid PIA 8303 and perhaps would have avoided this as well.
I recall one of the best TED Talks ever - "On Being Wrong" a must watch I recommend to anyone wondering how errors occur. The core problem is that being wrong feels just the same as being right. Discovering one is wrong is what feels bad, but until then there may be no push to confirm the belief is correct. By adding out-of-channel feedback it avoids a contaminated channel from interfering with understanding.
From what I have read here, it's possible the PF noticed that there had been no expected trim change that should have happened from the flap change, but didn't understand that some other change had occurred, and repeated the request which then did get followed. Had "FEATHER 1, FEATHER 2" been announced instead then both pilots would have looked to see why that happened.