It not incorrect.
Assault gun where not tank and did not move in close with troops. The fired from a distance where the lack of turret did not make difference. The fire they provided could be direct or indirect.
Stug-E had a gun with high elevation and could fire both direct and indirect fire.
When German where low on tanks and tried to use assault gun as tanks they vehicle failed in the role.
"Assault guns" provide support fire for the infatry to "assault" rather then do the assault themselves.
Assault guns, like StuG-E or StuH were used as DIRECT FIRE infantry support.
Only later StuGs were refitted with anti tank guns and used as poor mans tanks.
Their whole concept started as support guns moving in WITH infantry against entrenched infantry and fortifications.
Western allies have used infantry support tanks instead as they weren't concerned as much with costs as germany.
Soviets however were all over the place, with direct, indirect, casemate and tank mounted howitzers, low and high velocity guns used as both, direct and indirect support pieces.
KV-2(which is also an assault gun, that designation is primarily used to describe application of the direct fire unit and its, most of the time, high explosive armament tailored to kill fortifications) was actually used directly with infantry, just like short barreled StuGs were.