This "stupid thing" was the right thing to do for end users. They come to our website to see pictures of properties they are looking for. We just made them ~100px wider. They were literally smaller than a 256x256 map tile. It also matches the image thumbnail sizes of its sister site as well (which were already larger), which was mentioned specifically at the end of the article (I doubt you made it that far).
Beyond that, page speed is a ranking factor in Google, so it's absolutely not "stupid" to pay attention to it and make small changes that improve it: https://searchengineland.com/google-speed-update-page-speed-...