Compairing leig and usf mortar is kind of weird.
Hm... why do you think so?
I mean, sure there are some differences here and there (like range, firing rate, penetration, etc), but both indirect-fire support weapons.
Lets be honest, everyone used both LeIG and PackHowi against infantry, MGs and countering emplacements, garrisoned units. Just as if it would be a mortar. Even tho it is able to penetrate light armor, it is not its main role. I personally never felt like, oh my opponent built 222's, quick i need a PackHowi here...
On the otherhand, since USF mortar has been implemented, i think no one ever bothered to build a PackHowi. So those two must be related afterall..