That the Vulcans and the Romulans have incredibly close levels of technology is surprising, yes; but not nearly as surprising as the idea that the Humans, the Klingons, the Betazoids, and about a hundred or so other species all have such incredibly similar technology levels, and all without any hint of shared history before they developed their seperate warp drives.
Aww, maybe we should control for the Mysterious Space Police culling thing, and then the results would diverge like preschoolers let out on a May day. Like, there's a Prime Prime Directive. The MSP didn't apprehend Nero (natch), and look what happened?!
...I'm making a fully general counterargument, aren't I?:)
Here's another installment of rationality quotes. The usual rules apply: