It is much more likely that there were two types, normal genotype 62 and the mutant with the fluted edges. Ivins could have grown some out and then cherry picked one or the other to send in as his first sample. Especially if they can be distinguished morphologically on a streak plate.
If there were four markers on one genetic mutant, which I think is the case, but not so stated in your post, it could have some via the 1990 package. If there are 5 different kinds then not.
In any case, one needs to eliminate ISU as the source before any conclusion can be made.
If you have 13 lime green Chevy sedans and one of them robs a drive through bank, leaving some lime green Chevy paint on the side of the bank, and you can find only 12 that are unmarked, and the owner of the 13th one takes it to the crusher the next day......you draw your own conclusions.
I'm sticking to my guns and they are loaded.
Interesting general science article.