Yes. In a narrow technological definition of "final", you're right. However, not in the societal or legal sense.
You could just as easily say that cash payments aren't final because you could lose your wallet after you put the cash in it, but using the example of Bitcoin and the federal government is going to get more clicks.
Wasn't the point that a certain amount of ambiguity around finality is the usual (and natural) state of payment systems?