JSON, as used in VSC, can be defined as "plain text file containing an object", as configuration files have a hash map as root-level object.
AFAIK the difference between JSON (as used in VSC) and a Javascript object are minimal (no quoting for keys, possibly minor other differences) and using a JS object should have significant advantages in order to replace a de-facto standard.
`Template literals ie- multiline strings without needing escape or newline characters is a signficant advantage of JS object over JSON`
some will argue that scripting would thus be possible if the config was simply JS but that is a rabbit hole both on the debate itself and then the potential compexlity of config; there are trade-offs for/against but not a settled matter IMO as there are major projects like neovim that support full fledged config scripting (in the case of neovim they allow use of Lua)
AFAIK the difference between JSON (as used in VSC) and a Javascript object are minimal (no quoting for keys, possibly minor other differences) and using a JS object should have significant advantages in order to replace a de-facto standard.