Unlabeled buttons are bad for accessibility, see missing label:

https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/google_assistant_page/google_assistant_page.html?rcl=454ac851a4b0d5063c418968ce381766868183de&l=38

Please add an automated test when fixing issue to prevent regressions. See:
https://www.chromium.org/developers/accessibility/testing/axe-core