This post is quite dated, but I'll chime in.
There are quite alot of factors that go into the strategy of 1 ref VS 2. Me personally, I never saw the benefit to less than 2 refineries in Tib Sun.
In Red Alert 2, it's different because the miners dump their ore immediately, and they waste no time getting out of the refinery. In that sense, it's reasonable to have 2 ore refineries, one near one ore field, and one near the other, since all Miners are in and out so fast, but you have infinite storage, so the second ore refinery is more for the convenience of your miners than anything else.
Tiberian Sun has completely different mechanics. Not only do you have finite resources you can hold, but harvesters take forever compared to RA2 to dump Tiberium into the refinery. You need 2 Refs close by so harvesters can effectively line up, and keep a stable flow of credits in, while having a fair pool of credits to work with, so you're not working with minimal credits. If you have only 1 refinery, assuming you have about 3 Harvesters going, Harvesters will be waiting in line more than dumping or harvesting Tiberium, and that's not an effective use of their time, and you'll only have a pool of about 3k credits to work with, as opposed to 5-6k, and if you focus on only harvesting Blue Tiberium, that's double the value. Furthermore, if you don't have sufficient Tiberium storage via refineries and silos, your Harvesters will dump Tiberium, but you won't receive any of it. It's dumb, I know, and they fixed this in C&C 3, but all the more reason to build one more Refinery.
The real question is, when do you build that second refinery? Personally, I build my second right after my War Factory, training Infantry to defend as necessary while my War Factory pumps out a few Harvesters. Once I have 4-5 Harvesters and 2 Refs, my economy is set. I just pump out what units I need at that point. Or, if you think you need units, or you want to win with a rush, then 1 Refinery is unfortunately the best bet until later when you hear EVA/CABAL say "InSuFfIcIeNt FuNdS", but if that rush fails, neither do you have the resources, nor the units to continue fighting, and your opponent not only has a few forces left standing, but a VERY stable economy compared to you.
Some of it is situational, but some of it IS skill-based complete with the knowledge of how this game works, and what's expected in a standard game. The 1 Ref strat doesn't shock me as much because at some point I'm sure EVERYONE (including myself) thought one refinery was all we needed in our RTS C&C careers, but it does mean they're either trying something wacky, or not as experienced as some of the old-school Veterans of this game.
I hope that if none of the above posts answered your question (some of them were good), then this does.