A RESTful service is (usually as of today) a JSON API. They aren’t mutually exclusive things.

There’s no black and white definition there.

However, when someone is creating a RESTful service, they’re stating that they’ll be paying mind to HTTP Verbs and status codes as a fundamental part of their design.

In the original image posted, that dev clearly wasn’t paying mind to the HTTP layer and as such a commenter called it just a “JSON API”, which is the catchall, ugly, Wild West, typical way of doing things (always return 200, errors are in the json).

Once again tho, it’s not black and white. Others can and will disagree and want to be pedantic. I’ve been a professional dev for 35 years, devs love to argue abt this shit.