"Variable Ballistics" is a little trick where the round flies with something slightly different from the traditional parabolic arc, like a pitcher throwing a curve ball to confuse the batter. Maybe the gunner shooting the round knows what it's going to do and factors it in, maybe the thing has some doohickey inside that steers it off path then brings it back on path, I don't know - but an enemy tracking the round on radar is going to have a harder time tracing it back to its source because it isn't flying the way an ordinary artillery round does, so that enemy's going to have a harder time hitting you back with counterbattery fire. Doesn't affect point defense.
Striker Book-1, Rule 26: Counter Battery Fire
"If counter battery radar is available, it can be used to locate enemy indirect fire weapons. Location of the site of the enemy weapons allows a player to use that site as the intended point of impact of an artillery fire mission.
"A. Location: The die rolls to locate various types of weapons are listed for radars of each tech level in Book 3. If the rounds fired have variable ballistics (see Book 3) there is a DM (either + or -) of twice the difference in tech levels between the radar and the weapon; if the rounds fired do not have variable ballistics, the weapon's tech level is considered to be 7 (even if it is actually less)."
The DM for variable ballistics kicks in at TL 8, so yes it starts at the same tech level. As far as I know, you don't have to have laser guidance to have variable ballistics; it's just that the price is figured as 1/10 the cost of laser guidance. Saved them the trouble of taking up space with a whole nuther table.