“In this story, the hunter had a .30-06, totally inadequate for grizzly.”
The 30-06 has killed plenty of griz. but is not a good “stopper” in the case of an attack. With the right bullets and shot placement it is adequate, but there is little margin for error. I personally wouldn’t risk it.
My bear hunting buddy tells me that most guides won’t go out with you for grizz with .30-06. Too dangerous: The round is simply too small.
He has taken a grizz in Allaska with his .30-06 but it took three perfectly placed heart lung shots to bring him down. A very tough animal.
.45-70 is minimum.