But that isn't the point. If company A used the same circuit

Do you mean 'topology' rather than circuit?

Yes.


Did you read the Wikipedia link BTW?

I browsed it. I agree that there is a meaningful difference between G and H.
(I would never buy an amplifer whose output-stage voltage varied in a large
number of steps. It bothers me, for reasons too complex to explain briefly.)

I also read the Class D section. The author does not describe Class D as
digital. He says...

"Class D amplifiers can be controlled by either analog or digital circuits.
The digital control introduces additional distortion called quantization
error caused by its conversion of the input signal to a digital value."

and

"The letter D used to designate this amplifier class is simply the next
letter after C, and does not stand for digital. Class D and Class E
amplifiers are sometimes mistakenly described as "digital" because the
output waveform superficially resembles a pulse-train of digital symbols,
but a Class D amplifier merely converts an input waveform into a
continuously pulse-width modulated (square wave) analog signal. (A digital
waveform would be pulse-code modulated.)"

Except for the last sentence, this is a correct statement.