Currently sparkies have equal GuardScanRadius (GSR) to engineers, which results in sparkies being worse at reclaiming when attack moving or patrolling when enemies are nearby.
Guard scan radius is the distance a unit will initiate pursuit of enemies/reclaim from their patrol or attack move route. Its the reason why when you give an attack move engys may run backwards to get the trees behind them or branch off to get reclaim adjacent to the route.
The issue with Sparkies and having an equivalent GSR to engys is that, the sparky will switch from reclaim mode, to attack mode. Once an enemy enters the 26 radius, and the sparky is not actively sucking up a prop for reclaim, it will beeline for the enemy to engage in combat and stop reclaiming.
Reducing the GSR to 8, is a trade off, that makes the unit require more precision in patrol and A-move orders, but will not enter pursuit mode until a unit gets within 8 range.
This leaves a nice 8-18 range where the sparky will defend itself from enemies while still reclaiming.
The change makes sparkies worse at reclaiming uncontested, and with imprecise orders. Yet better at reclaiming when a enemies or engys are within 26-8 distance of it.