Nobody truly understands this basic thing called money, but for what its worth, here is my view.
The premise that a perfect monetary unit should remain constant relative to any particular commodity or basket in not well-founded in (esp Austrian) economics. All prices are floating, including money in terms of other goods, as the demand for money shifts with society's needs for liquidity and consumption patterns. There is also no impermeable anchor of value, as the mix of commodities or products/services within an economy is constantly changing, as are technologies and economic participants over generations, that does not allow any valid quantification of the relative value of any good between distant points in time. Any form of CPI is useless as such an anchor, and often open to distortion.
As an example of a complication, imagine you tied the value of a monetary unit to a basket of consumption goods. Then there is a productivity breakthrough with the promise of a preferred mix of goods in the future versus now. Naturally the price of consumption goods should fall, and capital goods rise, as money flows toward less consumption and greater investment for the future. The statement that money has in any way changed value does not make sense, only the price structure in the economy has changed to incentivise resource movement. Inflating the supply of the currency to compensate for the fall in consumer CPI would add no benefit whatsoever, and potentially lead to gross distortions throughout the structure of prices in the economy and result in mal-investment.
Currency becomes money (the most stable source of value) when its total supply is forcibly stable and it is the most marketable and widely acceptable commodity in the economy. The focus should be on conferring the right qualities on money, not in deliberately tying its value to something. Savers will be happier knowing they always own X% of the currency, for whatever that buys in the current economy, rather than knowing they can afford the same basket of obsolete consumer goods they might have wanted 10 years ago, even though their wants are completely different now.