Board Thread:Episode Discussion/@comment-24573226-20170121144613/@comment-26397825-20170122175850

It is based on their personality; Ren was often overcome by fear, but he'd recently had a nudge to work through it. So his semblance is suppressing that fear so he can move on.

I'm just saying I personally would like it if it also includes some presence suppressing abilities, to make it more useful in avoiding detection by Grimm through their normal eyesight and hearing.