_Do not ever ride downhill with wide open throttle on a two-stroke. You will sieze your engine for sure._
I thought it was the opposite - that you didn't want to do extended downhills at CLOSED throttle, since you aren't getting any oil at that point into the cylinder - that makes more sense.
I understand you should "burp" the throttle on downhills to keep it lubed. Going up and down hills without lubrication - also referred to as "dry humping" - can be painful. Always use lube for a smooth ride.