The robots.txt file should be used to restrict (and, in some cases, slow down) crawling at the time it is being crawled, not for SEO or for restricting access to mirrors or for any other purpose. It should never apply retroactively. (Unfortunately it is sometimes used badly despite this.)

People always use that link as reference to say that Internet Archive ignores robots.txt but it only actually says they are ignoring it for government sites. It suggests that they might do it for other sites in the future (of 2017), but does not actually say that that they have done it.

https://blog.archive.org/2018/04/24/addressing-recent-claims... which is a year later mentions that they have an automated process which is still following robots.txt for displaying old pages where the robots.txt was added later.

https://help.archive.org/help/using-the-wayback-machine/ does say they follow it for scraping, but this is phrased in such a way that would still be true for past sites whether or not they changed the policy. There is a page https://www.sysjolt.com/2021/archive-org-no-longer-honors-ro... which claims they don't follow it, but the site owner misspelled "robots" as "robot".