I have also contacted [email protected], and they have replied with a solution that worked for me.
“Thanks for reaching out!
WordPress added a feature in 5.3 that automatically creates a “-scaled” version of your images when they have a width or height larger than 2560 pixels. For such images, WordPress will serve the scaled version instead of when it needs to show the original, it will not use the actual original image. This scaled version will be compressed by the plugin if you enable the original to be compressed.
If you want the original image to be compressed instead of the scaled version, you can disable the scaled image creation by WordPress and have the resizing being done by the plugin. This way you will not have both an optimized scaled version and an unoptimized original version on the server. See for example https://darkog.com/blog/how-to-disable-wordpress-5-3-image-downscaling-feature on how to disable the creation of a -scaled version.”
