I made some experiments, and the problem definitely exists.

The results (length of the result, each time much smaller than expected):
with reverseOrder=True
    revCount=500 -> 1393
    revCount=5000 -> 500
    revCount=50 -> infinite loop?

with reverseOrder=False
    revCount=500 -> 61
    revCount=5000 -> 61
    revCount=50 -> infinite loop?

I am not sure if the problem is in Pywiki or API, but without API I got another wrong result (997).
Maybe something is hidden in http://en.wikipedia.org/w/index.php?title=Special:Log&page=Barack+Obama? Pending changes?
I'll try to continue tomorrow, but I am afraid that I will miss admin rights. When I tried to get API results directly in browser, it crashed.

In huwiki it seems to work.
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