Answer to your questions
Here's some info that hopefully answers your questions,
1) Although snow was predicted, the deicing fluid that's used most widely (Type II) has a holdover time of less than 45 minutes. If you deiced the aircraft, loaded the passengers you would need to deice the aircraft again.
2) The system you describe (Car Wash Style) is in use in airports in the US but not widely used. The method that was used on the aircraft that you were on is most popular as it can be done on stand, any stand. It is far more economical with fluid, and is more reliable, in that the person who is deicing can concentrate on areas that has more snow / ice than less covered areas.
Hope these answers help. If you would like me to elaborate more, please feel free to ask!!