... it’s important to remember that API design isn’t strictly about the practical implications on client and server software. The audience for an API is the developer who is going to consume it. Per the "principle of least astonishment," developers will have an easier time learning and understanding an API if it follows the same conventions as other APIs they’re familiar with.

https://blogs.dropbox.com/developers/2015/04/how-many-http-status-codes-should-your-api-use/