I don’t know if those statistics and data are correct, because I believe is just an estimate and we definitely have more than that amount of bitcoin Holders/Users. There are some underground Bitcoin users that or just dormant holders but even if we haven’t yet reached one billion holder/Users at the moment I doubt if this would take long before we reach that figure.
if we are talking about actual holders of bitcoin with actual UTXO signing privilege to actually make a transactions on the actual bitcoin network..
well you just have to count the UTXO as the max amount of potential holders ..
obviously some users have more then 1 UTXO to their name so there are less people than the UTXO count
as for other people that are using balance in centralised exchanges.. or altnet tokens representing something.. well its a simple "not their key, not their coin."
there might be many suggested 'hundreds of millions' of people with 'wallets' and custodial balance, and altnet tokens.
but there are a massive difference between bitcoin holders vs central service balance/altnet token users
i know some will say even if you have a altnet token or a centralised exchange balance your "still a bitcoiner" but thats for a lengthy debate (emphasis on holders using the bitcoin network)