Yeah, an inside the park homerun is impressive, but it falls under things like Unassisted Triple Plays that are still just one-time things, not a sustained achievement.
The only comparable offensive stat to a perfect game I can think of is hitting for the cycle and, to be honest, that's an odd stat that rewards achieving less. Four homeruns is more important than hitting for the cycle. In fact, hitting any homerun that bats in more than yourself is technically more important. It's only the precision of doing things that is praised there.