In my opinion, Bitcoin is the ultimate fiat currency, since it has no inherent value (you can can't use it for anything other than paying someone else bitcoin). It is a currency issued by "decree" through a protocol enforcing a consensus of users and miners.
The term "fiat" in this context describes the root of the
value of a currency, not its issuance.
And the root of the value is? Without a network of computers and people and businesses willing to trade it for something of value, what exactly is that value?