^ This is correct. Consider someone whose primary residence increases in assessed value from $100,000 to $1M. While living in the same home, the person's life remains unchanged as a result of the increase in valuation, except that their tax assessment may rise. The property tax effect is one form of forced realization, that produces an (unwanted) change in a person's life.
Similarly, if a home equity loan is secured, the person's life is changed through the spending that results, and is always accompanied by interest payments, even if there is no spending of the corpus of the loan.
Unless one's life is changed in some real way, there is no "realization". Tax and other spending, transfers to other forms, and exchange are different manifestations of a "realization" having occurred.
The only forms of real wealth are tangible property. Cash is very, very close, because even though a fiat currency is just government debt, it can quickly be efficiently converted to tangible property.
Consider that $1M home--it can quickly become the basis for either a reverse mortgage or a HELOC, or it can quickly become cash, which can quickly be traded for other tangible property.
Intangible rights count only to the extent that they can be effected, which means that there is a market for them--a buyer, and a reliable mechanism of exchange and enforcement. Real property is a hybrid, because depending on the jurisdiction, it is heavily dependent on the registration and legal documentation, and is heavily regulated.
So while tangible property is #1, cash is #1.5, and real property is #2, equities and bonds are WAY farther down the line.
Try getting a loan using the "unrealized value" of your equities for collateral, and see what kind of a deal you can get--if you get any deal at all.