> Is there a log of who instigated a wayback archive? Could they have been a different group doing what this person was?

Yes, IA now has a "About this capture" popdown at the far right of the injected toolbar. The first ever capture and some of the subsequent captures for one of the sites was from Alexa Crawls, provided by Alexa Internet; some later captures were from a "Survey Crawl" based on "a list of every host in the wayback machine". So this is basically automated, long-tail vacuum cleaning work.