I actually think it talking about a case where the rotator and the rotated are both in same place security wise, Like a schedule task to change login salt, both

I actually think it talking about a case where the rotator and the rotated are both in same place security wise, Like a schedule task to change login salt, both on the same vm\docker etc. Same goes to 2 apps connecting with a shared secret, making both of them change it wont expose any more components but will add additional layer of security (like google authenticator)