Save File Question

So I have 2 save files on my console. I play on a Ps4. In one save file I just play the game. Single character, pretty large house. The other save was simple so I could build the entire neighborhood of Newcrest. My question is, why are both save files the exact same size in my playstation storage information? I thought the save files were completely separate from each other? If so, I can't see that a single house and character could possibly add up to being the same size as 15 decorated lots and a single character. Is this a playstation thing perhaps? Thank you.