They're saying that gold is a cryptocurrency-like asset. Gold's value is primarily that looks cool and it serves as proof of work: the work of finding, mining, and processing it.

So basically, cryptocurrency (i.e. proof of work limited shiny token) has "a long history of a solid investment that goes back to ancient times on a global scale"

Gold's value stems from its unique properties as a metal and of its scarcicity.

Bitcoin’s value stems from its unique properties as a digital network and of its scarcity.

What would those unique properties be?

Permissionless, as in don’t need anyone’s approval and anyone can participate, transfer of value backed by trustless, as in don’t need to trust anyone’s word for it, global consensus system.

This applies to every single cryptocurrency out there, it's not unique to Bitcoin.

According to the ancestor post, gold's unique practical properties (like for electronics) constitute very little of its market value. Most of its value comes from its unique property of looking pretty and its scarcity due to work needed to obtain it, which is again the same as cryptocurrency.