My guess is that "Federal officials" would NOT be investigating if this were just a trivial dose exposure.
Ever heard of 50/50/90 Norm? You are wrong. Personnel get a larger uptake when placing nozzle dams in SG's at some plants. This is because it has been determined to be ALARA. Dose is Dose, whether it comes externally or internally.
The reason this is such a big deal is because it was a UNPLANNED exposure. That the NRC frowns on. It goes back to the old saying "If one can't do small projects correctly how can they be expected to perform the larger projects correctly?".
Michael D. Kent