The thing is that all you mention comes only from Koenigsegg's marketing. That's the exact problem that I and many other people here have - that Koenigsegg are very averse to any form of independent testing. Last time they did that was in 2007 with the CCX.
This latest lap time is just another serving of that. Even just from the start, doing a factory lap on a track where only independent laps exist is meaningless, because your lap would be several seconds quicker. More than that, they did it on a track which has basically no lap times at all. We don't know if the time they quote for the GT3RS is accurate, we don't know which version of the GT3RS it is, we don't know on what tires it was or who drove it. So really, this comparison doesn't tell us literally anything.
Now, it might very well be (and, frankly, it better) that the Jesko is much faster the GT3RS (991.2?), but the fact remains that this does little to actually prove that. If they want to demonstrate how fast the Jesko is, either go to the N-ring where it can at least be compared to other factory laps, or lend it to some publication for independent testing. Surely, if the Jesko is so fast and great, Koenigsegg should be eager to show it off.
Same goes for all the other stuff, like their gearbox, the build quality, reliability, etc. None of that proven at all, but still already hailed as "genius" and "superior" just on the basis of watching a Koenigsegg marketing video where they say it is.