In the mid '60's, the older buildings at BAe Filton had signs on the roof to warn people not to walk on the asbestos roof but to use the duck boards instead. Since that was a bit pre-google I guess they had no way of telling if they were using incorrect terminology.
One day, in the not too distant future, every time the tide comes in they may earn the name I called them then you will be glad you fitted them and you can laugh at your neighbours who are without.