"font-display: optional" doesn't work in Chrome in Next.js and Emotion project

I have a strange case of font-display: optional not working in Chrome browser (Version 91.0.4472.114 (Official Build) (x86_64)).

Few words about the project - it's Next.js app with SSR and using Emotion for styling.

Here's an example of how fonts are used in the app:

import React from 'react';
import App from 'next/app';
import { Global, css } from '@emotion/core';
import { ThemeProvider } from 'emotion-theming';

import theme from './path/to/custom/theme';

export default class CustomApp extends App {
  render() {
    const { Component, pageProps } = this.props;

    return (
      <ThemeProvider theme={theme}>
        <Global
          styles={css`
            /* latin-ext */
            @font-face {
              font-family: 'Zen Tokyo Zoo';
              font-style: normal;
              font-weight: 400;
              font-display: optional;
              src: url(https://fonts.gstatic.com/s/zentokyozoo/v1/NGSyv5ffC0J_BK6aFNtr6sRvwaRkREW-emmbxg.woff2)
                format('woff2');
              unicode-range: U+0100-024F, U+0259, U+1E00-1EFF, U+2020,
                U+20A0-20AB, U+20AD-20CF, U+2113, U+2C60-2C7F, U+A720-A7FF;
            }
            /* latin */
            @font-face {
              font-family: 'Zen Tokyo Zoo';
              font-style: normal;
              font-weight: 400;
              font-display: optional;
              src: url(https://fonts.gstatic.com/s/zentokyozoo/v1/NGSyv5ffC0J_BK6aFNtr6sRvwapkREW-emk.woff2)
                format('woff2');
              unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC,
                U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122,
                U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
            }

            body {
              font-weight: 400;
              font-family: 'Zen Tokyo Zoo', Monaco, sans-serif;
              font-feature-settings: 'kern';
              -webkit-font-smoothing: antialiased;
              -moz-osx-font-smoothing: grayscale;
              text-rendering: optimizeLegibility;
            }
          `}
        />
        <Component {...pageProps} />
      </ThemeProvider>
    );
  }
}

Example GIF (notice how font is changing despite being optional and cache being disabled) -

Did anyone also experience similar problem? Thanks in advance!