Normally only new pages are available for patrolling or autopatrol, but I see many entries in the patrol log where bots create a new claim and this is marked as autopatrolled (since bots hav the autopatrol flag). An example:
10:39, 19 April 2013 VIAFbot (talk | contribs | block) automatically marked revision 27230780 of page Colin McWilliam (Q5145398) patrolled
You can see in the history of the article,
that this edit added a claim but certainly did not create the page. Here's the claim creation itself:
The side effect of this is that the logging table is filled with these things. It's already up to almost 27 million log entries, the vast majority of them bots marking themselves as autopatrolled. In comparison, en wp has around 48.5 million log entries, and it's been running a whole lot longer with a much larger editor base.
If there is some compelling reason for having this patrol setup, then it should at least be documented in giant letters someplace obvious.
See also: T19237
**Update:** The wikidata logging table is now up to 606,370,402 rows, as of January 2018.