Gold and precious stones can also be mediums of exchange. That doesn't make them currency.
A currency has to be widely accepted as a medium of exchange, and it has to have a relatively stable value. Bitcoin fails bitterly at both of these. And experiments with bitcoin payments in the mainstream quickly failed (Steam, Tesla).
Your definition of a currency is incorrect. Many fiat currencies have experienced rapid devaluations (hyperinflation) while still being recognized as currencies. El Salvador has recognized Bitcoin as legal tender, so it also has at least some recognition as a currency. The IRS has not updated its guidance.
A currency has to be widely accepted as a medium of exchange, and it has to have a relatively stable value. Bitcoin fails bitterly at both of these. And experiments with bitcoin payments in the mainstream quickly failed (Steam, Tesla).