I expect economics textbooks in the future will refer to this time as the time this question was settled: were shells and gold money because of their intrinsic ability to be used as jewelry etc., or was it jewelry because their other properties (particularly scarcity / unforgeable costliness) made them natural monies?

Hard money advocates have been arguing this point recently, and IMO it can only be settled by the market and observation. Only if the latter is true, does Bitcoin have a valid claim to become money.