Recording events like scram throttle levels, and animations such as Gear position, trim, and flight controls,etc, needs to be handled in the vessels .dll. Orbiter records vessel position and rotation info, and thruster levels for normal engines like Mains, Retro, Hover, and RCS. Scram engines, or any other engine that doesn't behave like a regular rocket engine, aren't directly handled by the Orbiter core so they aren't recorded by the core.
Orbiter allows individual vessels to record any info they need, including animation states, special engine controls, engine gimbaling, even fuel levels. How much is recorded is up to the developer, but recording more increases the amount of code needed. For instance, to record gear status, the vessel needs to save that info during the recording callback, and also deal with this info when it's received during a playback call.
The DG-IV, like many vessels, doesn't record any animation states. The stock DG, and the XR series, record most animation states so gear will retract, aerobrakes will deploy, etc.