This is true about any asset that's not undergoing hyperinflation itself including stocks, bonds, commodities, real-estate, and foreign currencies. What's special about cryptocurrencies in this regard?
Stocks and bonds are not bearer assets, so you have to sell them before spending them.
Commodities are inconvenient to carry (though in some cases maybe more convenient than wheelbarrowing cash).
Real-estate is much less liquid, you can't sell or spend 0.01% of an apartment.
This is objectively false given that the article is about how easy it is to scam people out of their bitcoins.