We've already gone over this though (see earlier comments regarding foam/head aspect, etc); it may not be you were understanding what I'm saying because it's not about 'beers can be served in all types of glasses and sizes'.
I would say if people are really really really interested they could conduct their own field study. At places they go where they order beer, order both draft and then order bottle every time and measure each and every time over multiple establishments to compare the two. I'm guessing people will find inconsistencies all over.