At least P-40, P-15 and OSA SOC should not be immune(still P-40 performed well in OAF, I think)...
Yes, but keep in mind, that originally SAMSIM is created as a fire control radar (fcr) simulator, never intended to fully simulate the capabilities of any target acquisition radar (tar). Tar indicator was just shown as an information source only for the fco, not simulated "realistic to the switch".
This approach changed with the introduction of the OSA system, that has self integrated tar, so its capabilities had to be simulated much more accurately than ever planned earlier, with "indicator only" independent tar's.
From programming point of view, the SOC still use a completely different code section (object) than the rest of the fcr's, and ARM part is completely missing from it.