HTML AAM has been updated to map the s element to role=deletion with Chromium and Gecko having implemented this change.

ARIA in HTML is being updated w3c/html-aria#466 to reflect this change

Previously any role was allowed for the s element. That is still true but for the fact that like other elements with implicit roles it is now 'not recommended' for devs to use role=deletion on the element since it will already expose that.

The validator can surface this as a warning, as it does for other similar elements.