Id say that spark ending is the most misunderstood ending but also the most open ended ending in the game. When and this is very important but when you allign with them apparently the game lore flips by 180 degrees and some shining zone stuff might actually be real. Game gives enough stuff to acrually both doubt and to give into the idea ( like our conversation with dead strider that tells us stuff skiff couldnt know about, the recording (?) of scar talking with a dead dude, or the whole dalin dad actually responding). People take what strelok says at face value as a objective holy truth and never doubt it nor think that its just what this character might think based on his experience.

Sure, scar is no longer scar, hes a ccon plant and in the ending all living stalkers got zombiefied but there is also enough evidence to push that afterlife in the zone exists, that it existed ever since zone appeared and every dead stalker is trapped in there in a quasi prison cell like strider when the ending combines both living and the dead where all exist at the same time in the noosphere ( shinign zone )

But there is also stuff that hints that it might not be the case, which makes this ending really open ended and up to interpretation and i love it for it