Ending Status Codes for Benefits

Are there any "watch outs" for not using the TRX and TRT ending enrollment status codes consistently?

Specifically, is the TRX ending enrollment status supposed to be used ONLY when an employee's benefit is ending due to termination of employment?   

Sometimes I see the the TRX being used when the employee is not terminated, but the benefit enrollment has terminated and was not transferred to another plan. In this case, I would have thought TRT would have been more appropriate since the employee is still employed.

Example: 
Employee is enrolled in Dental plan but decides to end this coverage and opt out of dental coverage.  Shouldn't the dental plan have a TRT end status even though we aren't enrolling or transferring him to a new plan......In reality they are still  "transferring" from being enrolled to opting out.