[nyrikki]

First time I have ever heard someone say my Minimoog, OB8, Prophet and modular synths weren't synthesis.

ADSR is subtractive even if you ignore the filter.

The (ideal) square wave contains the odd-integer harmonic frequencies, where the (ideal) sawtooth has all harmonic frequencies.

I think starting in the digital world may make this less clear?

You are subtracting overtones from a non-sinusoidal set, the sound synthesis in subtractive synths is the more like choosing digits to construct a representable number.

Additive synths are actually far more restricted...remember that the set of computable numbers is not quite as small as the cantor set, but is getting there.