I usually have a hard time understanding how this type of data are gotten because there are many people who still store their Bitcoin in centralised exchanges. These Bitcoin will be regarded belonging to the exchange and they will not be added according to the number of people that own them. Of we add those Bitcoin ownership that are in CEX, ot will be obvious that more than 4% of the world's population have Bitcoin.
This is actually a great question which I didn't consider myself either. We certainly cannot be sure whether this data is accurate, although from my perspective it seems like a plausible scenario. The OP has quoted a few sources which claim they've been collected from Crypto.com and the Nakamoto (I'm not familiar with the latter). Does that mean they've been collected through centralised exchanges? Because if so, the actual number is then certainly higher than 4%. I'm also guessing that they're seeing it from the total addresses that hold Bitcoin, there's no accurate way of knowing such a number.