Thanks so much for such a detailed post, it was very clear to follow 
One thing that I see from the logs is that the SonarLint setting you have provided is not taken into account, and SonarLint tries to detect the node version all by itself. Usually, when the sonarlint.pathToNodeExecutable setting is taken into account, logs should include a line like Node.js path provided by configuration: /Users/Katie/.volta/bin/node.
the fact that the error is only shown for JSON and not Python files is expected since Node.js is a requirement only for SonarJS analyzer (JSON, YAML, TS, JS, etc… file analysis).
From your screenshot, it seems like you are using VSCode settings sync like this user. So, it could be that we have a problem properly handling synced settings 
Could you please confirm that is the case? Or whether there is anything “special” in your setup?
I will try to set up settings sync on my side and reproduce the issue.
All the best,
Sophio