This is what I was thinking of today. Metadata, yes, but what if I take another photo and edit it? I have a couple of phones, for work and home, I shall try to experiment. I usually edit the photos or may take the photo of a photo and edit on my favorite one. Google would keep Metadata of the one you sent. Further, if you delete the initial from the cloud, but keep the second photo and edit it, what does it tell? (I am making it too complex today).
I'll bet that it would depend on how it was edited and where, what software was used, etc., and the new edited version could then contain identifying information about the person's device doing the edits.
I just opened a photo I took with my Nikon camera last week and looked at the various very detailed metadata, which includes my name, date and time taken, GPS location, etc. I resized that image in Photoshop Elements and resaved it under a new name using the "save as for web" feature. Closed the file and reopened it. Was surprised to see no meta data at all other than my name in the new version, and date and time saved.
EDITED TO ADD - Interesting, too, as I also did a test where I did one minor edit to a camera photo in Photoshop Elements and saved it under a new name, and this time it DID keep all of the camera metadata, so perhaps it depends on the type of edit.
Aha! The method of saving does seems to affect the metadata. If I save as a jpg, it retains the camera metadata, but if I "Save as for web" (which is another method of saving as a jpg, but provides you with a smaller, more compressed version) it strips most of the metadata out.
I also took a screenshot of the same image and looked at the metadata for that, which was pretty sparse. I saved it, closed it and reopened it, and it tells me the date and time I saved it, and that I used Photoshop Elements 2023 to save it, but nothing else.