Your guess is correct. From this (annoyingly politicized) article,

http://retractionwatch.com/2014/07/18/the-camel-doesnt-have-...

... comes the following quote from the author of the camel-humps paper:

"I presented our latest results about 18 months ago at a PPIG workshop/conference in the UK. I felt it was helpful, since the claims I made had provoked hostility to the work, to retract those claims verbally. It had a dramatic effect, to the good. But I found (how I know is the confidential bit) that there are people who didn’t hear that retraction, and who are still hostile; and that hostility is doing harm. So I decided to retract more publicly.

"Interestingly, one person who I would have counted previously as hostile heard (indirectly) of the verbal retraction, and this summer was more than supportive. Research inspired by our work is going forward. So the retraction was worthwhile."

So, confirmed: there was an angry backlash, and this retraction is an attempt to calm people down.

You're right that this article is a bit hard to read in places. But as for your "reading between the lines", give me some reason to believe you're not just projecting your pre-existing assumptions onto this article. What did he actually say that let you read between the lines.

The reasons were in my post:

He has no real criticism of his original article. What he says about it is incoherent, not merely hard to read, as I point out in my comment.

And he makes reference to nature vs nurture, which is completely irrelevant to the actual issue, and only makes sense in the context of a political apology.

The whole "our statisticians didn't find my claims supported by the evidence" didn't seem relevant?

where does he say that specifically? He refers to statisticians helping to do further analysis on the data, but I don't see where they showed that the main claim (that the test is predictive of success in the course) is refuted by statisticians.