I was TRI/TRE on the 328 for several years, but I never heard of a case where the E/P brake lever was unintentionally moved back in flight while tuning the RMU or typing something into the FMS. There is a lot of load on it keeping it in the most forward position, and I don't think anyone could move it without noticing it.

I heard of a captain who wanted to show his F/O how to transfer hydraulic fluid between the two hydraulic systems by pumping the E/P brake lever in flight (this is a QRH procedure in case of a certain hydraulic problem!), and unfortunately he forgot to move it out of the "park" position after the demonstration. They landed with the brakes on, blew all four tyres and stopped right on the centreline. The wind was calm that day, so it's hard to say if the outcome would have been different with a gusty crosswind, which can be very tricky on the 328 due to the narrow wheel base.

Regarding the spin-down time of the propeller: Once the condition lever is pulled to fuel-off, the prop normally stops within 10 to 15 seconds (depending on wind). It seems as if the evacuation was initiated right after engine shutdown, and these people were very lucky not to stumble, because the propeller is very close to the main entrance door.

Quite amazing though, how quickly the other prop came off...!