In reply to Michael.

Agreed, all the extra generated images is crazy. And it sounds like core is concerned about that in this instance. But there are problem with OTF processing so not sure I’d vote for that.

What I can’t believe is a solution like Delicious Brains developed and promoted for inclusion in WP core wasn’t considered. And they did this five years ago! https://deliciousbrains.com/introducing-wp-image-processing-queue/

To me that seems the ideal solution. Images are generated and stored on the server but ONLY after they are needed. I don’t need a banner size crop of every single image I upload for example. 🙂