These ability are NOT "exactly the same" and actually their quite different:
Ostheer:
Name: "Hull Down"
Duration: None
Cost: Free
-25% received damage.
+25% weapon range.
Vehicle can't move.
KV-2
Name: "Firing Positions!"
Duration: Toggle Ability
Cost: Free
+30 maximum range. (+75% weapon range)
+25 minimum range.
KV-2 is immobile in siege mode.
One one is doctrinal ability taking up a slot and the other is ability always available to the specific unit.
There is no "received accuracy penalty" it has been patched out around three years ago.
Wehr """""commander slot"""" ability grants the ability on all tanks, including the ELEFANT
The hulldown has none of the drawbacks of the siege mode, except immobility (but you can immediately cancel it), it grants only buffs.
Also - the "75%" weapon range doesn't mean much when the elefant, a 70+ range TD, gets 25% larger range, which already puts it at a more or less same range as the kv-2, a pak-43 on wheels, you could say
Just because its a "commander ability" doesn't make it not strong, its not as strong, game-trivializing and bullshit as spotting scopes, but its definitely underrated