I do agree that it's their a**es on the line, but try to get a different trim on a typical 25-minutes low-cost 737/Dash8 turnaround! Not easy if PAX are already boarded and luggage loaded by the time you bring your loadsheet to the CPT. Only alternative then: reseat PAX (yes, you can expect grumbling).
A while ago we received a MVT message for an I/B Dash8 which explained its T/O delay as "CPT requested perfect trim". As I was due to arrive that very flight and turn it around, I made sure that I could come out with an acceptable trim on the O/B!
I would never question the CPT's right to request another trim, but I would make sure that the reason for the dealy is mentioned on the Flight Info Sheet and that the delay is 65, NOT 32!
Cheers