Cutting edge research indeed. We need to spread the news, tell all the parents that carrying kids helps sooth them. There is no way that parents could have come up and tried this on their own.
Actually, you could say the same about all manners of recording history; Story telling, art, education, music.
Why bother with any of it if people can figure it out for themselves? Because we progress further when we work as a team and share knowledge.
In general, I recommend taking all advice with a grain of salt: not because it is bad advice, but because no kids are the same, and what works with one will not necessarily work with another. Just take it easy and try to not worry too much. The unbroken chain of your ancestors have all figured it out, and so can you. And congratulations!
If you go from walking to putting the baby down horizontally, the baby will often be awakened by the sensation of falling backwards, and wake up.
Do you have children of your own?
That step is apparently not super obvious because this grabbed over 300 upvotes on HN, no small feat.
Even if it was obvious to some, parents of newborns are often (always?) sleep-deprived, so it might be hard for them to remember how well it worked to hold the baby still for 2, 4, or 6 minutes. I didn't have especially difficult sleepers, but it would have been nice to have seen this data back when we had tiny ones.