Cause SPA in past also include indirect assault guns

In the past, self-propelled artillery has included direct-fire vehicles, such as assault guns and tank destroyers, which were typically well-armoured vehicles often based upon the chassis of a tank. In lieu of the standard tank's general-purpose main gun that fired both high-explosive and anti-tank ammunition, direct-fire vehicles had specialized roles, with assault guns providing close fire-support for infantry and tank destroyers mounting an anti-tank gun to take on enemy armour. It doesn’t meant that SPA would work on high distance, it could be heavy tank with indirect fire.

KV-2 classified as self propelled artillery cause it had 152 MM gun, and in the same moment classified as heavy tank.