High score for blurred image ssim metric

vision
1

I think SSIM sometimes scores higher in Blurred images than in some clear images.

I want to mention the problem with this SSIM, but I don’t know why.

Can you tell me why SSIM gets a higher score on the blurred image?

This is Paper Example
image

(https://www.researchgate.net/figure/Comparison-of-SSIM-and-MSE-performances-for-Einstein-image-altered-with-different_fig5_283461887)

I think h image so claer than g Image but ssim metric high score of g image