You're probably right, but "was a developed nation" seems confusing it it's own way, given that the definition of "developed" is pretty starkly different across times (there is no country left in the world with infant mortality as bad as best performer US in 1900, for example). In long form, it was at the same level as familiar W.E.I.R.D countries like the US, New Zealand and France, and then later fell behind.

Three worlds wasn't a great classification system when it was first devised, even. First world and second world made sense, lumping everything else into one category was pretty eurocentric and dismissive.