Vehicle Parts III With Rocket Assembly & Launch

I haven't unlocked mega vehicles yet on my save, but I've unlocked the rocket assembly and launch tech. However, the assembly needs vehicle parts 3 to be constructed, which is only unlocked via mega vehicles. Is this intentional?

I think it is. The rocket cart is a mega vehicle. However, it could be clarified by an explicit technology requirement. Alternatively, VP3 could be unlocked by the rocket depot technology.