I think the report is quite comprehensive and compares many things that humanity adopted and how fast it happened. While it might look like a failure that we're still so low in terms of the percentage of people using Bitcoin, these things do take time sometimes, and it's possible that decades are needed till be can truly talk about global adoption. It also means that Bitcoin hasn't failed yet in terms of global adoption and we might see 1 billion users or more within our livetimes. I am not sure it's going to happen, but I think it might, and I'd be happy to stick around to see it. That being said, Bitcoin curve over 10 years seems very different from those of top technologies, so perhaps the prognosis is too optimistic after all.

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)

More good news and mainstream media positive news but it seems that's not possible because of the banks will obviously oppose when they see their competitors gaining lots of investors. The people that are in this field really need to work to explain to the people they know what's bitcoins all about and how would it be a huge help for our money freedom. That's what makes people stick to it when they know exactly the point of having bitcoins as your assets because they really like when they have total control of their money rather than the banks who might gonna close any day from now.

Bitcoin simply isn't convenient enough for every day use. Some people (including myself) could say that Bitcoin wasn't designed for every day usage(despite what Satoshi was claiming in the whitepaper). The expectation of 1 billion daily Bitcoin users will never happen in reality and there's nothing wrong with that.
Nobody is saying that Bitcoin is supposed to be the number 1 global currency. I would be perfectly fine, even if Bitcoin never becomes truly mainstream.
I don't think that anyone could verify the accuracy of this statistical data, but 30 million people seems like a pretty good number for a 12 year old technology.
BTC reaching 1 billion active users seems more like a fantasy, rather than an achievable goal.