Arty ALWAYS had a +4, it also used to have a +7 in place for indirect attacks. So to your example
It makes a huge difference because a BA unit at long range under the first rule set is Base + 0 + AoE + TMM + BA + Terrain (so on average a 8 with no intervening terrain or a 5 if short range POI) or under the other rules as Base + 4 + AoE + BA + TMM + Terrain (a 12 on average with no intervening terrain or a 9 to hit the ground POI in short range with a direct fire).
Before Errata, shooting at BA (I don't know why you wouldn't shoot at the ground under it...) would have been 4+(skill)+4(Artillery Mod)+1(Battle Armor)+X(TMM), for a total of 9 minimum on a TMM 0 target. Shooting at BA now post errata is 4+(skill)+4(Artillery Mod)+1(AOE)+1(Battle Armor)+X(TMM) for a total of 10. However, if you shoot at a POI in either of these instances, it it 1 less minimum, because you're removing the BA target modifier (For 8 and 9 respectively).
Additionally however, a missed shot with an artillery does not deal 0 damage. It scatters, and may in fact still hit the targeted unit. 'Considered to be short range' would mean that SRT (short range targeting) would function however, if the rules are consistently applied, as an attack that is 'considered to be' a ground to air attack, is in actuality, a ground to air restricted attack.
Also, reading back over your post. I believe the AS Pg.42 and AS Pg. 73 rules sets are different rules for standard and advanced artillery, so you would use one or the other.