This term is true for Bitcoin as well. Both can be exchangeable with essential goods and they are acceptable in our society.
Do you know a lot of stores that sell eggs or flour for gold or Bitcoin?
Gold is valuable because it's rare and has a limited supply.
If you think that it's enough to qualify as digital gold, then Pokemon trading cards are also digital gold. Or World of Warcraft's currency.
People call Bitcoin digital gold, because they want to make an argument that it's a hedge against inflation. The problem is, Bitcoin is not showing any good correlation with inflation or other macroeconomic indicators, it's completely unpredictable. The main point of a hedge is to act predictably under some circumstances, and Bitcoin still can't do that.