Urls are kind of convenient for a lot of things like form parameters, #link into an app or page, etc. That's state. Adding a bit more state via json in a parameter or whatever is about as old as the web is. Mostly, url length restrictions are still a bit of a problem but you need really long urls these days to hit those with most browsers. But aside from that, it's just another way to store stuff between requests.
PS: and i curse the day the social media brainwashed marketing freak coined the term "deep link" to mean just a normal link as its supposed to work.
In a previous experiment, I created a simple webpage which renders media stored in the URL. This way, it's able to store and render images, audio, and even simple webpages and games. URLs can get quite long, so can store quite a bit of data.