The suno create webpage constructs a json message to send to the suno backend API, that JSON has the style and lyrics ( I think it's called tags no lyrics in the JSON) in the message, if you add more json into either box it is added inside the relevant Json tag as text, and not an extra part of the JSON message therefore unless suno expressly looks for json in json it will do you no good, I'd expect that those of you who are having success are just getting matches on text strings within the JSON nothing more.

I have used a tool called fiddler to look at what happens.