The load i am referring to is throttle opening which is measured by a tps in % or vacuum by the map sensor in pascal.
ignition curves for cr500 below
A 2stroke ignition sees most advance in the early parts of the rpm range (30 degrees) to get the exhaust temp high to maximize scavenging and drops after max torque to something like 9 degrees btdc to maximize over-rev, this is for a 2d map of coarse but you get the point.
I thought about this topic for a while and realized an expansion chamber's scavenging effect is optimized for a certain temp, so with less load you can effectively increase advance to increase exhaust temp for throttle response. under load you would retard to decrease temp to decrease chance of melting the piston
this is why i love 2strokes, deceptively complex bastards