Thanks for the replies and info, I was inspired to ask because I'm adding all new led wallpacks and a new photocell to directly control them on a shopping center for the first time versus back in the ol days when I had the photocell work only a lighting contactor. I never thought LED would be adopted so quickly!
As others have already said, it has to do with the way some electronic ballasts are designed. The early commercial use electronic ballasts that weighed pretty close to magnetic ballasts used a large choke to mitigate harmonics and those limited the amount of inrush current.
When you dump the clutch, the transaxle sees far more peak torque than it does after it is engaged. Some ballasts started to include inrush limiting such as PTC or start through a resistor and short the resistor with an electronic switch after a bit of delay. The inrush is hell on contactor as well as ballast components. The basic CFLs have no inrush mitigation at all and they sometimes have a quantity limit per circuit that is much lower than the added VA suggests. Going above that quantity risks activating magnetic trip.
High inrush LED ballast will dramatically reduce contact life and you may need to use a heavy duty relay or a contactor.
Forward phase dimmers control by delaying the switch-on after zero crossing every half cycle and does a hard switch-on every half cycle and I've seen some LED ballast draw as much as 10A pulse every half cycle while dimmed and this is actually stressful for dimmers even when they're derated 1:3 ratio. The bolts that attach your struts to chassis will see more repetitive impact force with stiffer suspension. Each LED ballast design has a different "stiffness" so the derating is to ensure reasonable reliability.
There's a lot more to read about here.
http://www.lrc.rpi.edu/programs/solidstate/assist/pdf/assist-TechNote-Dimming-InrushCurrent.pdf
