Sorry, life is not so simple, and you really can't tell.
It could have been an automatic process, or an editor's own initiative, or even a public-spirited visitor's report. (Each has its own advantages and disadvantages, and the ODP would be the poorer for the loss of any of them.)
There was a time when the automatic process only flagged the site, and editors had to visit and do the actual removal. This was obviously a high-priority task, but with millions of sites, a very labor-intensive one. So editors would make "flying visits" to categories just to clean up the "robozilla reds" ("robozilla" being the checker-spider). Obviously an editor would have VISITED the category, but there would be a good chance of him NOT doing anything except whacking the dead listings.
Our current new-and-mutated robozilla both remarks and removes listings, so the editor doesn't necessarily even fly by.
On the other hand, an editor can work for hours on many categories, merely canning spam without making ANY visible changes.
It all comes down to, there's just no telling what's being LOOKED at.