That is due to me having sent docs / photos / links since I got the phone. However those are the only ones that showed up. In order to get the full history back I restored the new phone from the icloud backup.
After that - still no photos tab with all photos dating back to 2015. I then went to settings > tapped my name at the very top > icloud > messages > sync now. This can take a while depending on how many messages you have saved in icloud and how long you have it set to save them for and the sync process for me took a few days to complete and required me to check multiple times a day because it will pause randomly for some reason. Once the sync was completed. I started to see the option to download the historical attachments under the info tab in each conversation.