So many academic-level studies for something that can readily be deduced from a simple look into the mirror?
_____
Indeed the point is that Iran is able to supply shells - manufactured domestically from scratch, at a fraction of the price considering exchange rates of the Rial. Plausible deniability will be greater than with the likes of UAV's.
This said beware of false allegations designed to demonize Iran with those segments of the (mostly western) public that have already been brainwashed by the dominant pro-Ukrainian narratives. To me, these news are more likely to be fake in both instances (drones & mortar shells), although there's a slight chance that they might turn out accurate after all.
In the case of UAV's, it won't be possible to dissimulate their use for any sustained period of time, so if in the next couple of weeks there's no visual evidence for Iranian drones in the Ukrainian theater, we may safely conclude that the US regime lied... again.