Did you not read what I wrote? OS X no longer has a concept of "Unsaved changes". It's always saving your file. You write in a new sentence, it saves it (virtually) instantly. The original file was already overwritten when you selected "Save As".
The new "Save As" just makes the old "Duplicate" more handy. I agree it's a poor choice of name, they should have kept it named "Duplicate".
Yeah, after reading your post twice and confirming with cat in the terminal it sort-of makes sense.
They still shouldn't list "Save as..." as a new feature, because it sounds like they made it work like every other OS.
Also, the textedit window is extremely deceiving when it shows "file1.txt - edited" -- when in fact the file has already been committed to the filesystem!!
Then save as should revert the original file to how it was when opened and create a new file with all the changes in that.
It should forget all the autosaves for the original file.
The new "Save As" just makes the old "Duplicate" more handy. I agree it's a poor choice of name, they should have kept it named "Duplicate".