Sounds like standard 737 winter ops procedures.
Flaps Up - Full - Up; checking that theres no jams in the mechanism due to ice that may have built up and that they're working ok through the full extension and retraction cycle.
Flaps up for taxi out is to ensure no contamination (e.g. snow thrown up by the wheels) gets jammed in the mechanism and to preserve the holdover time of the deicing fluid (tends to run off the flaps faster when they're in takeoff position). For this reason its desired to only set flaps for takeoff once takeoff is imminent.
Holding on the brakes while spooling up the engines; Boeing recommends a static run up, of 70% N1, for up to 30 seconds to ensure that any ice that may have built up on the fan blades during taxi is shed before commencing the takeoff roll.
So all in all, your crew did an excellent job, and I'd only suggest concern if they hadn't done any of what you describe.
