WOAI + default traffic in FSX

I use a combination of WOAI FS9 and FSX traffic files. I store the bgl files in a custom folder (not in scenery/world/scenery). This is a picture showing WOAI + FSX default traffic at default ENGM, which shouldn't be possible when using FS9 bgls.

I discovered however that if I disable my WOAI traffic scenery folder in the scenery library, then enable it again I will get both worlds, default + WOAI.

http://simmerhead.files.wordpress.com/2014/01/2014-1-6_20-6-32-686.jpg