It replaces them with different numbers, even if you don't try to do math on them :)

  echo 1.4e99999999999999 | jq
  1.7976931348623157e+308

While I agree that the meaning of json numbers exists, I'm not sure which JSON standard you're referring to that contains this meaning. json.org certainly does not contain it, and links to ECMA-404, which just says "JSON is agnostic about the semantics of numbers."