Yenn, you're correct for all the RV's except the 12. Vans manufacture and sell the RV-12 as a completed fly-away LSA (SLSA), and they also sell the kit which the builder can register either as an ELSA or an experimental (EAB). If it's built as an ELSA, which most of the ones in the USA seem to be, it has to be an exact copy of the original with no deviations, and Vans then remains the registered builder - even though they didn't (crazy system). Therefore, because it can be either an SLSA (factory built) or ELSA (homebuilt copy of the factory original), Vans has to provide the POH and acceptance test procedures, so they write and publish those documents. However, if you choose to build the kit as an experimental (EAB), then you can write your own POH as per the other RV's, but why would you when it comes with the kit anyway.
Incidentally to add to the craziness in the US, once the plane receives its `pink slip' for airworthiness as an ELSA, the real builder is allowed to modify it in any way they like, provided they don't violate the LSA performance or design parameters. In other words, it effectively becomes an experimental but with Vans still as the registered builder and with no control over any modifications. They must worry about that! Over here, CASA doesn't care whether you register it as an ELSA or ABE. If you build it as an ELSA, you're the builder, not Vans. Consequently most if not all 12's over here are built as ABE. In the US, the perception is that an ELSA will hold its value better, so that's the main reason most seem to go that way. It also only needs a 5 hour Phase 1 instead of 25 or 40 hrs, so that's another reason.