Huh?? What are you reading? The FARs are pretty clear that IFR
flight in class G is legal.

I'm reading NTSB reports, dude. ;-)

How could the NTSB say something that is clearly
explicitly allowed by the FAA is careless.

It's not expressly allowed, it's just not expressly forbidden.

I don't have a strong opinion either for or against their ruling.