Something doesn't stop being a premine once you sell it.
Once they've finished selling their premine to the public would it be accurate to say it wasn't premined at all? Of course not. So it's not accurate to exclude the partially sold portion now.
This massive understatement of their premine is a well known example of the dishonesty of ethereums operators and advocates.
Exactly. Selling a premine to "the public" is indistinguishable from selling only a fraction to the public, and the rest to yourself. While there is an opportunity cost to the latter, it may also serve to create an impression of large demand that further benefits the preminer.
Once they've finished selling their premine to the public would it be accurate to say it wasn't premined at all? Of course not. So it's not accurate to exclude the partially sold portion now.
This massive understatement of their premine is a well known example of the dishonesty of ethereums operators and advocates.