I have never heard of 6 traits either, but I do not teach English.
I am a Spanish teacher who learned the Collins method while
working at an all boys K-9 school. The boys there appreciated the
clarity of the Collins method, and because the school had embraced
it as a whole, they knew what the expectations would be from year
to year, not to panic about spelling during Type 1, etc. It
alleviated anxiety and promoted neat writing and creativity within
a clear set of standards. As a foreign language teacher, one of
the biggest challenges I face is the "bad at Spanish" mentality,
which effectively prevents them from taking in new information. I
ask for Type 1 and Type 2 writing on a regular basis because it
allows them to get ideas out using specific parameters. It may be
obvious, but it is standardized, and that really helps.