In SIP routing, Not registered type unable to select extension or sip devices, it displaying only PSTN

Steps :- 

1. login as customer.
2. go to sip devices.
3. click on advance routing.
4. now enable "not register" option and try to select extension or sip devices and observe.

Actual result :- In SIP routing, Not registered type unable to select extension or sip devices, it displaying only PSTN 

Expected result :-  It should be select both extension or PSTN type.

See videos or screenshot :-