if a non pilot is telling someone about how to operate a G-1000 or even a mechanic (non-CFI or GI) teaching systems at Simuflight, what is the difference?
Those instructors are authorized by the FAA under part 142 to give instruction it is not an apples to oranges comparison.
Anyone can teach anyone for anything they want. Whether that instruction can be applied for the requirements of a certificate or rating is the difference.
If you want split hairs feel free but this is a pretty obtuse argument going on.