At no point in the current expression you wrote "-", though. It may make sense that if you type [-] [2] [x^2] [=] then you get -(2²) = -4, but if your current answer is already -2, then tapping x² should result in (ans)^2 = (-2)^2 = 4. Splitting your current answer into a separate unary [-] as in - (2²) makes absolutely no sense.

Most calculators, even CAS ones, simply get this always right. But sadly this is not the first "desktop" calculator that I see getting this completely wrong. And it makes some results outright wrong!

"-4 makes sense if you consider that the calculator is so damn stupid it ignores every convention every single calculator has made in the past hundred years and instead copies behavior of a dumbass language" isn't exactly the praise you think it is.

I didn't enter -2, I calculated -2. The x² should have been taking x = (-2).

Python gets it right:

    >>> 2-4
    -2
    >>> _**2
    4

What? The person you're replying to isn't typing -2. He said explicitly what he is typing, and the result is unambiguously incorrect.