Not exactly. That is one of 3 wiring methods permitted. It does not require the use of listed PV conductors, it permits them along with nonmetallic jacketed multiconductor cables and conductors in raceways.
If you can tell me how it is possible to connect a string of panels on an array to an inverter using only jacketed multiconductor cables and conductors in raceways, I'll admit that PV wire is not 'exactly' required. As far as I can see, PV wire with a crimped on solar connector (e.g. MC4, Tyco, etc.) is the only thing that you'll be able to use to directly connect to existing panel products. (On grounded systems, also USE-2.) From there you can take it a very short distance to a J-Box and transition to something else, if you wish, and do this for each home run. But if you've got the PV wire I don't know why you'd do that.
Why is it that I typically see USE-2 chosen as a popular choice for PV cables as opposed to other conductors that may be sunlight resistant and rated for wet locations?
I'd say it's because 690.31(B) explicitly permits it, nothing else besides PV wire is explicitly permitted for solar in the code, and PV wire is more expensive.
So if the module conductors are routed in an raceway does that mean they can technically be of THHN type?
Strictly speaking, for wet locations (i.e. on the roof) you need THWN or THHW or something else marked with a W. (see 310.10 (C)). But most wire marked for THHN these days is marked for THWN as well. (Again, though, you'll need some PV wire to get from the module to the J-Box at the start of the raceway.)