The behavior of the :sort /pattern/ command is inverted with regards to Vim's own implementation. Vim will skip the pattern while codemirror-vim will sort according to the pattern.
Vim documents its behavior in :help :sort:
Take, e.g. the following buffer:
With Vim's :%sort /./ (to skip the first character), the resulting sorting will be (correctly):
While codemirror-vim will sort (incorrectly) by the first character: