Yeah, helm is...interesting. it's just a gnarly yaml -> template -> yaml cycle. it's better than nothing for the problem it solves....but god, there's gotta be a better way.
At least with JSON, tooling can help you find invalid syntax in the middle of your file.
And JSON tooling/libraries (compared to YAML tooling/libraries) are usually faster, easier to use, have less bugs and present less incompatibilities between themselves most of the time.