Effectively there is a massive jungle of photos out there and your photos are sitting there in the wild. It is easy to test out (access a photo in google photos) there will be a long url name to access it (the name is a web link not a jpeg address by the way. Paste that into a file you write to a usb. Take the usb to a foreign computer you have not use and cut and then paste the url in a browser you have not used so It will not know your google ID. There is your photo! Other have noticed this issue.
This is a really big deal, A significant betrayal of my trust.
Whilst I intend to keep using google photos for my shared photos and images (mainly for my blog). I have already turned google photos off on my phone and I'm working through deleting a lot of photo from my google photos account.