The last attack, was it Napalm?
They didn't simply launch missiles at dead army just to demoralize an enemy, but maybe for clearing the battlefield from corpses?
for what it's worth, the US never signed the Dublin Convention on Cluster Munitions so it's technically possible that US troops stationed in Japan & isekai'ed are the the ones using the cluster MLRS to avoid any treaty breaking
They weren't going for suppressive fire, they were going for 'Ground Clearing'.
As for carpet bombing, that actually needs bombs dropped from aircraft.
Search up the Zelenopillya rocket attack,where the Russians ambushed a Ukrainian column and annihilated it using only MLRS. Fuck these things, if you get caught in that 1km your chance to survive isn't too good.