Since Apple hasn't seen fit to allow you to set the desired parameters when taking the picture, they had to provide that capability somewhere. Assuming it would make sense is folly as Apple has shown a tendency to make sharing files as painful as possible since the .mac format.What I find funny about that is Apple's Mail app on iOS gives you four size options when mailing photos.
Now with the new format, I hope they offer some format conversion as well as I have seen only one Windows tool that purportedly deals with HEIF files (XN View 2.42) while HEVC is getting to some traction among the shareware titles (though I haven't verified that they can handle Apple's implementation of HEVC). I hope Handbrake support is available.