In addition to what others wrote, here's a practical example:

I wanted to insert an old photo in a comment, from my Google Photos. The photo doesn't exist on my device, since it was taken from an old phone. I located the photo in Goolge Photos and downloaded it to my device. Then I went to pick the photo in Sync, but it was neither visible under "recent", nor in any of the albums. So I had no choice but to scroll thru hundreds of photos to manually look for it, and found it under the original date the photo was taken - which makes sense, but in the previous gallery, my recently downloaded photos would appear at the top.

I've only got a few hundreds of photos so this isn't a big issue for me, but I can imagine it'll be a dealbreaker for people with thousands of photos on their device.