I agree. And the thought of a total change in the composition of the product (glass to metal, etc.) to achieve 1.5mm is somewhat disturbing to me.
Don't want to be alarmist, but one of the overarching themes at Apple during the current renessaince has been that Ives rules first, and the engineers had to adapt the technology to fit his style. Going from glass to metal seems like a nod to engineering over style, IMO.
I'll be more concerned if they start using plastic.