I also caught them in SEMRush and there are a lot of them. I assume when they migrated the site they didn't bother with all the images and just 301ed them in a big batch later when they saw an issue in search console.
The question is, is it worth getting the developers to update all the imgs. I agree, ideally it should be done, just from a practical and time-consuming perspective, I know they are going to ask me whether it really matters.