Can some one help our disagreement involving my pedantic grammar nerd partner.

He always used to choose/get given the cappuccino chocolate bar out of the Thornton's Chocolate 3 for 2 offer when sharing with his siblings - back when it only cost £1!
He is a super grammar nerd and will pull me up on every little mistake - but I'm not too sure he's right here.

He says that it is correct to say "I have always been the cappuccino one." Indicating that he always had that particular chocolate bar. Saying "the 'one' means that it claims he is receiving the chocolate bar".

However, I have been telling him that grammatically that sentence means that he IS the cappuccino chocolate bar and whilst we probably would hear the sentence and understand what others mean, we should, if not wanting to be lazy with grammar, say "I have always been (the one given) the cappuccino one" or "I have always been (the one to choose) the cappuccino one".

Now we are disagreeing and neither of us can back up our points properly or know who's right (the winner gets the cappuccino bar - or gets to be it!).

Help please!