[breadbox]

Not quite. Achilles and the Tortoise originally came from an essay by Lewis Carroll. Hofstadter had borrowed them for GEB, and in doing so also borrowed their gender -- or so he thought. In reality when he went back to check, long after publication, he realized that Lewis Carroll had left the Tortoise completely genderless.

[wazoox]

I dug up the book to check, and in the 20th anniversary preface page 16 and 17, a few lines before the previous quote there is :

"Mr Tortoise, meet Madame Tortue A few years later, a wholly unexpected chance came along to make amends, at least in part, for my sexist sin."

And here comes the French translators part:"[...] they rather gingerly asked me if I would ever consider letting them switch the Tortoise's sex to female."

So I don't see what's the contradiction you're trying to point out.

[breadbox]

Then it's probably my mix-up. An extremely similar passage occurs in Metamagical Themas, in which Hofstadter describes a conversation in which he first realized that he may have only assumed that Carroll's Tortoise was male. I've likely confused one with the other.