The rules restricting fire from only refer to building locations, not building hexes. Although there are restrictions on the size of a gun that can enter a rubble location, most mortars are allowed.
Again, I point you to B23.423
And the rule does not refer to building Locations when restricting fire, it refers to
buildings.
Now we know an upper level Rubble Location is no longer a Building Location. However that doesn't mean it is no longer part of a
building hex or of a
building.
See also the B24.12 EX "Hex 6J8 is a third level building which has just been rubbled from the second level up"
Now maybe B23.423 should have errata , e.g. change "upper level of a building" to upper level building Location" but at this point in time, it doesn't.
I believe a Perry Sez would be needed to allow a 5/8" weapon to be in an upper Level Rubble Location.
Your interpretation would allow the following situation to occur:
Using the 23.22 illustration of a two story house, assume the Level 1 Location of bulding hex G1 is rubbled. The ground level Location of G1 is NOT Fortified. In an adjacent open ground hex, are two German squads, a crew, and a 75L Pak 40 AT Gun [M#8].
Mph 1: The crew and squads try to push the Gun into the ground level of bulding G1 [M#8, Manhandling DRMs +4 {2MF entry cost doubled}, +2 hex tem, -4 for the additinal two pushing squads, so net Manhandling DRM is +2
They will get the AT gun into the building on a DR of 6 or less.
MPh 2: Now by your reasoning, the upper level of G1 is not a building Location or a building. So there is no reason why the Gun can not be pushed to the upper level Rubble Location
So M#8, DRMs +3 wooden rubble tem, +6 {rubble stairwell cost of 3MF, then doubled}, -4 two additional squads pushing, for a net DRM of +5. So a DR of 3 gets the gun upstairs [A DR of 5 or less if needed if a Low Ammo counter is placed on the Gun]. If there was enough time, you could get it there on a DR 7, with a -2 labour staus counter
Are you saying you believe that to be correct, that a non- large target AT Gun can be Pushed to an upper Level Rubble Location and then fired from there?
Cheers
Jon