Would be useful if we can create more than one trunk with same username. Sometimes we can have a same trunk to be user by more tah one tenant, so, we can create the trunk and limit the number of channels of it. Example, one trunk that support 2 channels, we can create 2 of them, limiting to 1 channel each.
For MT environments we thoroughly recommend creating trunks in the Main Tenant and then share with others. Besides, in the most recent versions of VitalPBX and the MT module is possible to limit the number of concurrent calls per-tenant basis.