It seems obvious the deck was built afterwards.
Hope this doesn't scare you! If you look at the primary side of a transformer, then you will see that the wire may be smaller. It's all calculated to work. The POCO knows what their wire can handle. They are normally involved to make sure that the existing secondary can handle any new loads being added--based on a number of factors.
Giving thanks to Nikola Tesla!
The wire on the primary side is smaller because there is less current, hopefully the POCO knows what they are doing! :grin: