The level of detail in the article is insufficient for us to be arguing over this.
But having worked on government software projects before, I am aware that some fraction of them are dominated by office politics and contractor ass-covering rather than any desire to provide some benefit to the public in exchange for its tax dollars.
Absent any additional facts that would contradict, my default assumption is that peon employee was reamed for making his superiors look bad, rather than any genuine technical or legal limitation.
Here's what I saw in my head.
Dev: Mind if I watch how you use this program for a bit?
911: Nah. Slow today.
Dev: Hey, what's that mean there?
911: That's a priority call.
Dev: What's the difference.
911: Real emergencies, instead of cat stuck up a tree type calls.
Dev: People actually call 911 for that?
911: You have no idea. People call when their drive-through order is wrong.
Dev: Wouldn't it help if those were, like, highlighted, or something?
911: Yeah, but they told us it couldn't be done on this system.
Dev: I bet I could do it.
(30 minutes later)
Dev: See, look. I knew I could do it.
911: That's great! Go show this to Mgr!
Dev: Hello Mgr, look what I did! The dispatchers love it!
Mgr: You're a loose cannon, Dev! Turn in your badge and gun right now!
Dev: Wait... what?
Mgr: You have to follow the rules in this department, Maverick. Lives are at stake!
Dev: I literally feel like you are speaking a different language right now.
Mgr: If you so much as pick your own nose without approval, your ass is mine.
Dev: I'll just be going now, thanks.
In this fictional scenario, the boss isn't mad because the dev changed the system, but because he had already told people that what was done was impossible, or had to wait years until the next major upgrade version. The end-users discover that there is a layer of resistance between them and the developers, which exists only to resist change and make it more expensive. When someone sees that a feature they have previously been denied can be implemented by some punk kid the same day, it undermines the authority of management.
And it interferes with that deal where management enters the feature request on behalf of the end-users, the crony-packed development contractor quotes eight weeks and $50000 for it, and some punk kid still does it in one day, but with a bunch of other people skimming off the top at taxpayer expense. That gets rolled into a periodic upgrade package that the end-users are conditioned to fear, because it always interferes with their work for at least a week.
That's just the stuff I make up in my head when I don't know the whole story, because that's what matches up with my anecdotal life experience.