Achievement data is a percentage. Since there were no giveaways, PS+, or Game Pass offerings to skew the data, there's no reason to believe that the percentage would change across other platforms or across people playing the game offline. The achievement we're using is the one for beating the game, as is the finite number of 1.3M that Larian offered in their infographic. Yes, that number does include early access purchases. Why wouldn't it? Those are still copies sold, and they're still included in achievement data.