Hi there,
X/Pro uses its own registered image sizes to cover almost all devices without sacrificing the quality, example if the optimization tool suggested you to resize your image to 300px since it’s displayed on a container where it has 300px width, are you going to follow that? That’s because most mobile now has 767px and stretching a 300px on that device will make it blurry. And there are retina devices that even suggest for bigger and doubled size images.
This size https://abilitymagazine.com/wp-content/uploads/2017/06/War-on-disabilities.jpg is even ideal for desktop and tablets ( 1080px and it’s even small in large my screen ). But the tool suggested to compress it and save 88%. By means of compressing, you will need to resize it down or lower the quality. Maybe because it’s displayed on a 350px container and the tool expected it to be 350px image too. I’m not really sure how they calculate the optimization and compression, but it looks like it.
In responsive design, it will not always stay to 350px, it could change, it could increase or shrink down. And it looks the tools are only testing it on a specific device where it has a specific width. (eg. a standard mobile site like m.facebook.com where it’s actually a mobile site and not a responsive site)
But I don’t think it’s due to those images, according to PageSpeed result, almost all images are optimized except to those three, but, those three are loading fast once the page is loaded.
How about turning off Essential Grid and disable all tracking code and embed codes? The EG is throwing 404 error which affects loading speed. While those tracking and embed codes have delay time when connecting since it’s hosted outside of your site. Then test it again to see if there is any improvement.
Thanks.