It seems an easy miss, but then again it depends what the testers are testing exactly. Unless you’re constantly making realistic flights during the tests with set strong winds (or live weather on a windy day), it could go easily missed.
Like you, I immediately noticed the problem on my first take off from Barra. Well, rather I didn’t notice, unless I began my take-off run - and realised something was very wrong as my aircraft started veering 
Together with the flap bug introduced in World Update 3, after I turned 180° I was practically in a hover in the stiff winds.
I could report via Zendesk but based on RoyalTot’s reply above I assume they’ll make a general fix for windsocks so their rotation will be ignored or overridden in scenery files, or something to that effect.