The “readable indented text” refers to https://xenondata.org/#scalars where multiple lines of text can be indented and extracted as expected. One can argue that JSON is not readable due to requiring escaping (\n) for multiple line strings.
This is not enough of an improvement over JSON to justify choosing another format, given that the new format is (A) not recognized and (B) uses even more special characters. (By "not recognized" I actually mean there are no implementations given for any languages, much less accepted standard implementations.)