The name and basic description of RSO imply that the primary function of RSO is to improve something about resource spawning. Now, having used it for a while, I think that it is actually about trains, and only uses resource spawning as a means. I feel like a good one-liner description might be:

"Changes resource spawning to encourage large area logistics solutions involving trains."

The extended description touches on this, but if I had read that sentence in the in-game mod menu, I'd have had a much better idea of what the thematic function of RSO is, and it would have eased the decision of when to use it. Even the long description buries the lead if this is accurate.

On the other hand, if I'm mistaken, and RSO is about resources, then I am confused and curious about what the idea is.

Description of mod is what it was from the start I think.
It could use an update most likely - I'm better with software then natural language so never though about chaning it.
I was thinking about thumbnail too but didn't come up with anything nice.
And your understanding of mod role is correct - it's supposed to make trains mandatory. I think that starting area resources might be actually to generous - there were long discussions about that at some point.