Google's John Mueller said on that using the request indexing feature in Google Search Console's URL Inspection Tool does not change canonicalization. The question that was asked is if it can help speed up URL removal for a 301 redirected URL.
Jan Caerels asked "Clicking "Request indexing" on an old URL that was 301 redirected. Would that potentially speed up the process of removal?"
John Mueller from Google replied to that post on LinkedIn and said, "I doubt it." He added that "requesting indexing doesn't change canonicalization (and if anything, it almost seems like a sign that you'd want the initial URL indexed)."
He also wrote that if you do want to remove URLs from Google Search, to use the removal tool in Google Search Console.
John wrote:
If you want to remove it, I'd use the removal tools. If you want to nudge canonicalization one way or the other, I'd work to get more of the other canonicalization elements lined up better. A redirect doesn't guarantee canonicalization - for example, when a site redirects the root URL to a lower-level page, it often still makes sense to index the root URL.
Forum discussion at LinkedIn.