There's a small particle of truth in that:

Some people value the projected appreciation of the asset more than the immediate liquidation thereof.  When there's a spike in the value of an asset, whether it's Bitcoin or Google stock, the projected rate of return (relative to other assets) goes up, making "hoarding" more attractive.

However, on cannot get any tangible benefit from the appreciation of some Bitcoin without eventually spending it. 

In some ways, Bitcoin is demonstrating Gresham's law, as users who prefer it to fiat currencies keep the BTC somewhat out of circulation.