Capital gains absolutely have tax implications. Just like my house rising $100K in (unrealized) value over a year.

Capital gains receive favorable treatment under US tax code but are also a realized gain by definition. That is you actually have to sell the asset and are taxed based on any profit earned.

An increase in the estimates value of your real estate holdings does not trigger a capital gain. Your municipality, however, may use it as an excuse to increase their assessment of the value of your property, which is used to calculate the tax they charge.