I know you already referenced this before here, but do you have any idea why this happened? Is it just a marketing stratergy to sell the most amount of the higher models first? This can be the case, but not even develop any other models and only relying on the 2 higher models is kinda strange imo. Maybe the alloy versions are a lot easier to manufacture then the carbon ones and for that reason they didnt want to worry about them? Who knows ...With the original Mahle version (aborted) of the gen4 there wasn't even an alloy version in development, the gen3 was to run in parallel for the lower models.
This is just me thinking out loud, I have the idea that the comp alloy is the most sold model(?), to fully develop a bike without even considering it is strange ...