Very Old Phone with Photos

I was looking through our electronics to recycle and I came across some very old iPhones that we owned: 3G, 3GS, and two 4S's. I was going to recycle them, when I thought it prudent to check that they were factory reset first. After charging them, it turns out they were never wiped. So I have been pulling the photos off of them in preparation to reset the phones. The iPhone 3G has been stubborn. It's Settings->General->About page shows 2067 photos on the phone. The Photo app shows them being in two different categories: "Camera Roll" with 243 photos and "Photo Library" with the remaining 1824 photos. I've been able to extract the the Camera Roll, but I cannot seem to get the Photo Library off the phone. I have used iMazing to backup and extract data, but it has difficulty with the ancient iOS version of the phone [iOS 4.2.1 (8C148)]. Is there some way to get access to the Photo Library data on this phone? Maybe some old software or forensics software to access it? Or perhapse a way to upload this data to iCloud for access? Can anybody explain what the difference was between Camera Roll and Photo Library on these old devices?

Thanks