So in the USA you have commercial glider pilots who are not instructors but it's "easy" to get a CFIG rating (certified flying instructor, glider ???) if you've got a power CFI (certified flying instructor???) rating?
Very strange. It ain't like that in the UK.
CFI in the UK means Chief Flying Instructor, and his word goes. No arguments. You've got to get past him before you go anywhere near an instructor course.