[TextField] Problems with changing the input label fontSize

I tried to change the fontsize of the lable using

const theme = createTheme({
  components: {
    MuiInputLabel: {
      defaultProps: {
        sx: {
          fontSize: "13px",
        },
      },
    },
  },
});

Achieved

But On focusing the fontsize appears too small which make a empty space on the right (Look into pic below)

Please let me know how can I get Rid of it.
Or I can change the Font size only when the input is not focused.
What I wanted it to look like is
(Small font size when Field is empty)
and
(Normal font size when Field is Filled)

Originally posted by @iamadityaaz in https://github.com/mui/material-ui/issues/13840#issuecomment-1046002798

Start with the MuiInputLabel defaultProps and sx configuration shown in the issue, then inspect the TextField label behavior in its focused and filled states. Done means the label has the requested font size in each state without the unwanted empty space shown in the screenshots.