From a mathematical crypto standpoint it's sorta good, but again what value has been created? It's not like the blockchain is now saving us time and effort in factorization that can be applied to real world problems that would otherwise need to be recalculated regularly, which is a pity.

Of course you can truthfully say fiat currencies are totally notional, but as a practical matter the value of a fiat currency reposes economic stability and security offered by whatever government issues it (which may or may not be valued by other people).

A backed currency means another entity is willing to guarantee they will trade the currency for something else. In the example of the gold standard, this means the government would exchange dollars for a certain fixed amount of gold. This meant that dollars could be worth more than gold, but theoretically wouldn’t fall below their fixed value in gold, because at that point people would trade them in for the gold.

You can’t just redefine backed to mean something that is expensive to produce. If something is expensive to produce it also doesn’t mean it has any intrinsic value.

(I’m also not arguing that modern fiat currencies are backed - in fact they are not backed by definition! I just get frustrated by all the fake economic mumbo-jumbo about Bitcoin).

I used to be able to trade dollars for gold and vice versa, at a fixed price, guaranteed.

I can't trade bitcoin for 'math'. No-one is storing energy reserves in case there's a run on people converting bitcoin to energy. Bitcoin is not backed by anything.