I appreciate that thought, but this affects all images.
Imagine if the spoiler image was just a screenshot of an actual spoiler in a game or story.
At 85% scanline loaded, you can pretty much see the picture, and it doesn’t blur until fully loaded.
Thus the whole purpose is rendered ineffective.
Also, replies (the expand to show back and forward) don’t use the spoiler effect at all.
This is a bug that needs to be fixed, regardless of the content that this specific post contains.