Territory management and roles hierarchy

Territory management and roles hierarchy

Hi everyone,
we are facing a problem with territory management.

Our roles hierarchy is quite simple:
- Area sales managers
      - Sales executives (reporting to Area sales managers)
- Backoffice

"Sales executives" can see only accounts/contacts/etc based on their assigned territories, and this is OK.
Our problem is that Area sales managers can see accounts/contacts of EVERY sales executive, not just those related to their assigned territories.
Is this expected? How can we fix this, so that Area sales managers see only what pertains to them?

Thanks!