Exactly that, it's a Dash thing. For some reason it has a flight-taxi switch, which when selected to 'taxi' keeps the spoilers retracted. When selected to 'flight', if weight on wheels and power levers are retarded, Dash logic assumes that you are landing and therefore want the spoilers deployed. Once the power levers are advanced, it concludes that you want to go flying and retracts the spoilers.
Don't ask me why, I just drive it . . .