I've had the diamond breakfast benefit applied to room service once. However it was due to checking out of the hotel before the EL or restaurant was open. This was at the Conrad Tokyo. To be honest, I think it only happened because my Japanese friend was there when the FD explained my property benefits. When we got to the breakfast benefit, my friend started speaking Japanese to the FD. Afterwards, I was informed I had two options from the room service breakfast menu. On my receipt, there was no service charge.