The DC metro official rule could be read two ways:
During rush hour, the bicycle must be "folded or (disassembled and enclosed in carrying bags)"
During rush hour, the bicycle must be "(folded or disassembled) and enclosed in carrying bags"

I have been yelled at by the station manager after I rolled my bike into the station intending to fold/bag my bike on the platform before boarding the train. The policy is only for inside rail cars, not the platform. I do a reverse commute and there is really no need for this ridiculous policy.

DC Metro's policy:
Metro allows non-collapsible, conventional operational bicycles, as well as tandems, electric powered, and "opened" folding bicycles that meet the size restrictions inside railcars from Monday through Friday at any time except 7-10 a.m. and 4-7 p.m., all day on Saturday and Sunday, and all day on the following holidays: Martin Luther King's Birthday observed, Washington's Birthday observed, Memorial Day, Labor Day, Columbus Day observed, Veterans Day, Thanksgiving Day, Christmas Day, and New Year's Day. These bicycles shall not be allowed inside railcars on July 4th.

Folding bicycles and non-collapsible bicycles of all types that are folded or disassembled and enclosed in carrying bags, cases or boxes are deemed "luggage" items and are permitted inside railcars at all times. The carrying bags or cases must be made of a sturdy material such as canvas, nylon or leather-type materials.