The PerTenantExtensionCop is not producing errors if you add a field or enum value outside of your apps extension range. 

PerTenantExtensionCop analyzer (Microsoft.Dynamics.Nav.PerTenantExtensionCop) - enhancement to rule PTE0002.

Asking for a new capability equivalent to AppSourceCop's AS0013 own-range check to be added to PerTenantExtensionCop.

Review GitHub Issue here: https://github.com/microsoft/AL/issues/8313