Search on that page for: "Skeleton and Bone Metabolism". K1 and K2 work differently. We know a lot but there is still a lot more we don't know. Hell, looks like even different versions of K2 (from MK-4 to MK-13) works for different stuff in body. Only because MK-7 stays in blood for longer than MK-4 doesn't mean that it better. It could also mean that body is better in utilizing MK-4, or even that it's using it for different stuff.
More here: https://chrismasterjohnphd.com/2016/12/03/start-here-for-vit...