Frag assault launchers make the unit count as if it was armed with frag grenades, the vehicle can't use them in any way. At least, that the entry in my BA dex. That make any difference for you there, Magpie?
Yeh it means the grenades have a range of potentially 18" ! LOL
Seriously, though it is a stretch, the unit itself could be throwing grenades.
The launcher however does "function as a weapon"