Essentially, Krastorio 2 adds the resource "mineral water" which is separate from typical water. Tungsten requires this fluid while mining if Krastorio is present. Without RSO, mineral water can usually be found close by to the spawn, as its related technologies are red/green. With RSO, especially with large region sizes, mineral water can be very far away.
Without Tungsten present, lacking mineral water nearby to the spawn isn't that big of a concern, since it can be safely ignored until later in the Krastorio 2 progression. However, with Tungsten present, its suddenly necessary for basic fixtures such as lamps, and assembling machine 2s. This isn't an issue without RSO since mineral water tends to be fairly common. A small amount of Krastorio 2 mineral water added to the starting area would fix this. Even without Tungsten present, it wouldn't be game breaking.
