iPhone photo file sizes seem very small in iCloud

Yes the original is stored on iCloud as documented here -- iCloud Photo Library - Apple Support

File types that you can use with iCloud Photo Library

Your photos and videos are stored in iCloud exactly as you took them. All of your images are held in their original formats at full resolution — HEIF, JPEG, RAW, PNG, GIF, TIFF, HEVC, and MP4, as well as special formats you capture with your iPhone, like slo-mo, time-lapse, 4K videos, and Live Photos.

If you export the unmodified original (file menu ==> export) from Photos you will get this original photo

LN

When you download photos from the webpage www.icloud.com using the Photos.app, you will download the edited versions of your photos and not the originals. But Photos Library is storing the original image files, exactly as you imported them and uncompressed.

To convince yourself of the quality of your original photos, select a photo in Photos on your Mac and use the command "File > Export > Export unmodified original".

Compare the result to what you get when you export an edited version "File > Export > Export ... photos".

This dialog lets you select the size and quality of the exported file. Be sure to reveal the controls for he quality by clicking "v" to the right of "Kind: JPEG".

Of course if you export at a smaller size (small, medium or large) you will get a smaller photo - if you export the unmodified original you will get exactly that - if you export something else you will get something else - and your threadjacking is inappropriate, violates the TOU and has nothing to do with the original question which is confusing to everyone including you

LN

I'm having the same issue with an export of photos from the Photos app with other than original size.

When selecting a medium or large size for export, the photos and files become very small, much smaller than they used to be. I'm very puzzled about it and annoyed as it now need another editing step to scale original size photos to a smaller one.