It's just not as simple as setting a value in a field and making a phone call. As I understand it.
In the POTS system, an incoming call carries the callers phone number only, but not the name. The POTS provider is responsible for doing a database look up, locally, right when the call arrives at their switch and they then send the number and name down the analog phone line to the ringing handset. There are hundreds of these CNAM databases, Verizon has one (or many), and every 1000-user backwater mountain-town phone company has one (or more accurately they subscribe to one).
For what you are describing to happen means any SIP provider immediately accepts (perhaps when your SIP client registers with your SIP provider) any value in the field you show, and then immediately sends the value to all CNAM databases all across north america, and it all instantly works. Realistically speaking it doesn't work like that.
There are various discussions on here about how different VoIP providers handle just this situation, a few actually allow it (Voip.ms is one reported to do so), and many will reject the call if a non-blank name does not match what they already have on file.
Did you actually try this? Making a call to a POTS phone?
