> Why is the average bytes smaller? Shouldn't it be the same size file?
The content being encoded in the PNG was different ("https://www.reddit.com/r/rustjerk/top/?t=all" for the first, "https://youtu.be/cE0wfjsybIQ?t=74" for the second example - not sure whether the benchmark used different things?), so I'd expect the PNG buffer pixels to be different between those two images and thus the compressed image size to be a bit different, even if the compression levels of DEFLATE within the PNG were the same).
The content being encoded in the PNG was different ("https://www.reddit.com/r/rustjerk/top/?t=all" for the first, "https://youtu.be/cE0wfjsybIQ?t=74" for the second example - not sure whether the benchmark used different things?), so I'd expect the PNG buffer pixels to be different between those two images and thus the compressed image size to be a bit different, even if the compression levels of DEFLATE within the PNG were the same).