Woah, pretty extensive read. One thing I noticed though, is the author seems to assume that blockchain.com wallets is the only one available for Bitcoin users:
therefore, if 3 million active Bitcoin users represent about 17% of all Bitcoin owners, then the total number of Bitcoin owners around the world is only around 17.6 million.
He is quite right for that number of active users and I think it might be even an overstatement.
Let's say 3 million "active" bitcoin users, so that's at least 2 tx a month to qualify as active, it makes 6 million tx a month, 200k a day, that was the median for the last year.
And we have about 25 million addresses with a balance, since my two wallets have about 17 of those, it does fit.
Another good way to get an idea of active users is by checking the number of daily bitcoin transactions on the Blockchain website and also lookinh at the coinmarketcap website traffic check, things like that a little out the box lol but its actually very good for getting an understanding of the amount of current users.