I've been in a lot of decent sized grows using dehps here in colorado. My friend actually runs a DEHPS + CMH setup in his basement and his colas are redicuolously huge, but arent as dense as my LED grown buds grown under similar PPFD levels.
It's basic plant biology that longer internodal distance would cause the flowers to be less dense, as the internodes are where the buds start stacking from.
Im not making up shit bud. It's well known LEDs tend to grow denser flowers than HPS for this very reason. Why do you think sativa dominant plants don't have buds as dense as indicas? Because the internodes are more spread on sativas.