`never` result from `isDate` when value is `unknown`

[xiwcx]

Hi i'm getting the following error:

from the following code:

const getValue = (value: unknown) => {
  if (G.isDate(value)) return value.toISOString().split("T")[0];
  if (G.isNumber(value)) return value.toString();

  return value;
};

i'm not certain this is an error, but if is the expected result i am uncertain of why. if i change the input type to any then isNumber gives me a never result:

[JUSTIVE]

just curious, the current type of isDate is <A>(value:A) => value is Extract<A, Date>. why not just simply <A>(value:A) => value is Date? is there reason not to be?