I haven’t done extensive testing, but I’m 99% sure the fire damage from colossi is counting towards Spear of Adun damage.
In games without colossi, I usually average around 35k-40k Spear of Adun damage.
In games with colossi, I usually score between 70k and 80k.
This holds true even on Dead of Night, where I usually completely bypass Spear of Adun energy upgrades to get my 3/3 colossus/immortal ball up faster, and use the energy I do get to deal with the few air units that map has. I don’t think I’m getting 80k damage on a completely un-upgraded Spear of Adun by shooting mutas.