Corrigendum
I thought it was clarified in a previous post, but it seems it wasn't (truth be told it is dubious). You do not need to be native to get level 6 (as I thought originally) but the problem I have were I am is the system we use (it is not designed to prove up to level 6 but 5 only). I understand it has to do with how the test is designed and performed i.e. length, techniques/technologies used, etc.
I guess the confusion came as I was told back then, when I did the test, that it was a pity they couldn't give me a 6 (I guess if we could grant it here I may have got it, but that's blowing my own whistle and definitely not a fact).
So, apologies for the misunderstanding, but you can be 6 if your testing system is allowed to grant a level 6. Wether you're a native or not.
A.