I login in https://drive.google.com/, and click Google Photo item in left bar, then click "New" and select "File Upload" to upload a photo.
In my mind, I think the photo I just uploaded will list in both Google Photo item in Google Drive and "My Drive" -> "Google Photos" folder, but in fact, the photo don't list, why?
Must I upload photos via Google Photo https://photos.google.com/ ?
Best Answer
It appears that the Google Photos section within Google Drive is only a representation of the actual photos that were uploaded/added through that service/site.
Yes, you CAN add a photo to the Google Photos site, by adding it through Google Drive -- but that actual photo was NOT uploaded through the Photos service/site, so it will not appear in that section. It does appear within the normal Google Drive section though. And it will appear in the Google Photos site.
So yes, it does appear that in order for you to see photos within Google Drive > Google Photos ... then you will need to upload them using the Google Photos site.