Only Safari (maybe other WebKit browsers?) uses this for its UI. Since it only impacts UI, and only in one browser, it was removed from the spec in https://github.com/whatwg/html/pull/6482. Continuing to support title for these functions is not a spec violation, since browser UI is outside the scope of specs (i.e. web pages cannot observe Safari's use of the title argument). But, you might want to clean it up regardless. Especially if web developers only test in other browsers, and so pass strange values (e.g. "null" or similar) which Safari ends up displaying to users.
<rdar://problem/75695791>
https://html.spec.whatwg.org/multipage/nav-history-apis.html#the-history-interface
Pull request: https://github.com/WebKit/WebKit/pull/20404
Committed 273650@main (4ef4b65d33f4): <https://commits.webkit.org/273650@main> Reviewed commits have been landed. Closing PR #20404 and removing active labels.