It's worse than just liquidity, if he can unlock his wallet on his phone to verify it and its balance on the spot.... not only is it liquid but he's effectively carrying it on himself in cash at all times.

At least it's only $2.5 million or so remaining, since the rest is now likely in assets that require more effort than merely access to this person+phone (and attempts to rob a person of assets in a bank are usually more traceable than stealing bitcoin). Still seems a bit crazy though.

If he's smart he's storing his remaining balance in safety deposit boxes, etc rather than all on his phone.

Right. You can torture all of that wealth right out of him, pretty much on the spot.

The difference is that people who got rich through business are already well known, so it’s too late for them. This guy has the option to stay hidden, so he takes it.

People who make $25b are well known. People who make $25m in business are not.

On a side note, I recall a story told by Chris Pine being surprised by all of the bodyguards surrounding an extra on the set of Star Trek. That extra was Jeff Bezos who had a small part in the movie. Chris Pine had apparently never heard of him.

Not as well known as Elon Musk obviously but with 25 m in the bank you're unlikely to be completely invisible like this guy. Someone is bound to know you exist.