I see what you're getting at but the examples you give- everyone knows what all of those words mean. Someone may say "pop" but they still know what soda is. People who say "aks" are not confused by the word ask.
Well those weren't exhaustive examples, but I'd still disagree - for the longest time, I though "hoagie" was a polish food (I grew up in "grinder" territory) and I was mystified the first time someone asked me to pick up an "orange coke" at the drug store.
Another example: http://www.youtube.com/watch?v=03iwAY4KlIU it's all English, and you can often get a general meaning from context, but the vid gives examples of words I've never heard, or more familiar English words used in combinations that obscure the meaning. So of course you can take someone from the video and drop them in NYC and they'll be able to function, but there will likely be things they miss and things NYCers will miss talking to them. Now in a school environment, that can make a huge distance.
Further illustration: In my area, I hear both "sub" and "hoagie" used to refer to different varieties of the sandwich. I'm not positive what the dividing line is, but it seems like hoagies are generally less healthful than subs.
