You are correct.
Because God is outside of this universe, He Himself is not scientifically testable, because we are limited in our scope of observation, and this universe has limitations imposed by natural laws. Hence, He is inherently unknowable, outside of the following:
1. Special revelation.
2. General revelation.
Are you related to str.org? (!)
Yup. and as a gnostic, I go by the first.
No relation to the website, obviously. :-)
(some of their reasoning leaves a lot to be desired...)