TAG and Arty

[Centurian99]

So I see the other two answers on TAG after the 6th printing errata, but the answers don't seem to jive with the updated wording.

For reference:

TAG is used to paint a target with a laser to designate targets. A TAG-(or LTAG)-equipped unit can make a special weapons attack in order to designate a target. A TAG attack uses all appropriate rules for a standard weapon attack. LTAG works only at Short range, while TAG works at Short and Medium range . Designating a target is an additional attack that can be made in addition to any other weapon or physical attacks that same turn. The target of a painting attack need not be the same target used for the unit’s weapon or physical attacks. Unlike most effects, TAG designation takes place immediately and can be used by other attacks in the same turn, and only that turn.
A successfully designated target is spotted for indirect fire by the TAG-equipped unit, with no spotter attacked modifier. In addition, a designated target can be attacked by semi-guided LRMs (see p . 150) and homing artillery (see p . 152).

1) the other answers here seem to say that these rules don't apply to spotting for artillery or other ID fire...but why not?  The TAG rules clearly state that the designated target is spotted with no spotter attacked modifier.

2) There's also nothing that would seem prevent TAGging a point of impact.  The arty rules specify that the immobile modifier doesn't apply to the shooting the artillery itself, but why would that apply to the TAG.  So wouldn't the target number to TAG a POI be Skill + [0 or 2 (range)] - [4 (immobile)]?

[BrrtWarthog]

The answer is in the description:

A TAG-(or LTAG)-equipped unit can make a special weapons attack in order to designate a target.

The only rules that allow you to "target" the ground are the base arty rules (POI), but that's not a special weapons attack, it's an arty attack. There are no rules for making a special weapons attack against the ground, therefore you can't TAG the ground.

Also, you wouldn't get the -4 for an immobile target against the ground - "immobile" is a unit movement ability status. The ground isn't a unit, therefore it can't be immobile.