I CAN see the logic in, like--
So, the word 'image' keeps being used to describe Syaoran (and Sakura). We know Evil Wolverine used a mirror to clone them, though, which would make them specifically mirror images. And mirror images only exist as long as there is something to create a reflection, so when he's gone those reflections disappear as well.
I don't know if the Japanese word being translated as 'image' has the connotations of 'mirror image', but if it does that would make the whole thing make much more sense, and also feel less out of left field, imo. (and Syaoran dissolving into glass shards would also fit into the 'mirror image' theme!)
The mirror image idea DOES fit the scenario very nicely actually, I like that a lot. I kind of wish they had gone for that phrase in the end.
I'm not sure the logic entirely makes sense in my head with the Reincarnation at play, And with Yuuko and Clow paying their lives for it, but it's definitely a lot closer than it was before! Thank you for that.