Having a "fast engine", or "high motor" are just new phrases for being aggressive. There are also multiple ways a player cann be aggressive. Going strong to the hoop, attacking the glass, on-ball defensive pressure, diving for loose balls and the like a the ways I primarily think of.
Green, at best, shows "flashes" of these. He is b no means an aggressive player.
Ugh, I've enough excuses with this guy. He is what he is. Passive underachiever.