Makes resources more sparse than base game. You will need to use trains much earlier to get resources. Game will be more difficult especially with higher enemy settings.
Tweaks
Mod category: Tweaks
Small changes concerning balance, gameplay, or graphics.
I've had this issue ever since 2.0.1, although it has gotten better with the later versions. With the latest it seems more varied, so if you reload a few times you will likely get one where you have a little more room to play with. Altering the starting area size however does not appear to make a huge difference in RSO currently.
It definitely appears to be RSO related as vanilla Factorio starting areas seem to work as normal.