Once I realized that most likely I had to buy the F1 (even though it's a 5.62 weapon) in addition to the Nitro (sniper ammo), the M1A then popped up for purchase. Great!
I was assuming the progression would be by ammo type to stay in sync with the type which was available out in the region of Kyrat.
Surprisingly, and the main purpose for posting this, the M1A allows for a suppressor, so if that wasn't the intent, then I assume that should be corrected with any update - along with making the Warrior AK chamber the 7.62 ...
"The NUKE, are you crazy?" "Oh relax, it's got a very small yield. Just enough ..."