I'm pretty sure it has to be manually put like that by the dev, right? I've never seen bundles not-intentionally total up to really weird percentages like this. Always 10% 25% 50% etc, except when a dev is intentionally 69% off or w/e
Yes the dev sets the discount. They did for the base game with the 35% discount. There is also another buy option to get the game and soundtrack and you save 10%. Technically that buy option is also 35% off but once that is discounted, you also factor in the 10% discount savings for buying that bundle. In the end, you get the 41% off the original price off the bundle. Whether it was their intention or not, hard to say definitively cuz they can always say it's a "coincidence".