One could say AutoMath contains only mandatory functionality of the IEEE 754 floating point standard and Math contains the recommended stuff. Well almost.
IEEE 754 regards fma() as a fundamental operation, like abs() and sqrt(). The fma() routines are mandatory for an IEEE 754 compliant environment, not recommended. So for consistency, they arguably belong in the former.
My 2c. Not urgent.
Hi Damian —
I think this is a very reasonable question. If you want to champion the change, I'd suggest opening a GitHub issue for it—though this is a reasonable place to test the waters for such ideas… (though the number of people here who follow the IEEE 754 details may be ~1 
).
-Brad
He did so a while ago 
FMA missing from AutoMath · Issue #25605 · chapel-lang/chapel · GitHub
Lydia
Werp, my bad! (Good thing it's still not urgent? 
)
-Brad
I was trying to raise the profile by creating a Discourse item