weren't RLs retconned to be available way earlier?
More or less? Standard rocket launchers aren't available before the marians created them, but primitive rocket launchers are available all the way back to... I think pre spaceflight.
At the very least the earliest canonical unit to use them dates to the Terran Alliance era, and they're actually the only one shot missile system available during the succession wars.
They take a very minor hit to cluster table rolls, but it's actually so minor that on average it has almost no affect.