If I'm not logged in... I see the 65% off sale. If I am logged in, I see 95% sale. So perhaps it's because I own the original or perhaps it's just a glitch in the sale pricing. But it's definitely showing both and it's odd.
When I purchased (you can check it yourself by putting it in the cart), there was a notice that this promotion is not applicable to gifts. So it might be an intended special promotion for owners of the previous original version of the game. And Steam glitches out there maybe. If this price is available to you too, then I assume it's intended.