Search index purge when will it work?

I installed the Search index purge plug-in one year ago. There are still 968 image pages showing in Search Console as either not found (404) or as “Submitted URL has crawl issue”. These peaked at about 1030 some time last year.

On this page https://yoast.com/media-attachment-urls/ the text says:

“After six months the attachment URLs should be gone from the search results. You should then remove the search index purge plugin, and keep the redirect setting of the attachment URLs set to “Yes”.”

It’s been a year. Does this mean I have to be patient, or does it mean the purge isn’t going to work for me? Or have I done something wrong here?