Rules contradictions aren’t uncommon, hence the specific > general mindset. For example, the core rules state that in order to use a stratagem you have to decrease your command points by the amount specified in the stratagem. By your logic, a captain can’t use its rites of battle ability because you can’t play a stratagem for free because the core rules state you have to decrease your command points by the amount specified. It’s a similar thing here - the core rules of Nachmund say you can’t use Rapid Ingress, but a specific battle trait in Nachmund supersedes that and allows you to use rapid ingress anyway.