Recently while going through FRA security lines to get on a NW flight, men were asked to remove their jackets to go through the metal detector. One man's wife was asked to remove her fairly light sweater. However, a bunch of Arab women wearing head to toe long robes were not asked to remove their robes, though they were lightly wanded after going through the metal detector.
The man whose wife was asked to remove her sweater asked the security agent why he had to remove his jacket and his wife had to remove her sweater, but the women did not have to remove their long robes.
The FRA security agent said "that is airline policy"

1. Is it really airline "policy" that sweaters and jackets have to be removed but long robes do not (e.g., they could be removed in a private booth with a female security agent)? Or is it airport policy, e.g., perhaps in FRA or other European airports full of Muslims in robes?

2. If policy, is this a written policy or just random enforcement discretion (i.e., possible concern by the security agents that they would offend the Muslims, but not offend people being asked to take off jackets and sweaters, despite obvious reasons and need to find out what's under the robes)