Hi,
I figured out what the issue was. If the articles 2nd revision represents the page being moved, the rev_text_id is the same for the first 2 revisions.
When compressOld iterates over the revisions, a ConcatenatedGzipHistoryBlob is initially set to the first text row, but the 2nd revision also points to the same text row and compressOld overwrites the ConcatenatedGzipHistoryBlob with a HistoryBlobStub.
There was already a bug filed for this, I've updated it with more info and added a fix that works for us:
http://bugzilla.wikimedia.org/show_bug.cgi?id=4268
Thanks. Travis