Jamie,
I see the issue. Excel drops the text delimiters (guotes) from the first record. But I'm not sure exactly why it's an problem.
Excel removes the text delimiters when the file is opened, rather than when it's saved. When you save the file, a warning is displayed to let you know that if you choose to keep the CSV file format, some contents may be lost. Seems like Excel is providing lots of disclosure here.
It's also worth noting that Excel removes the text delimiters because they aren't needed. Text delimiters in a CSV file are typically used when there are symbols in the value that are also used as field delimiters (i.e., a comma). For instance, when I changed the first record in the sample CSV file to read
a,"This is some really, really, really long text"
and then attempted the experiement, Excel saved the text delimiters exactly as written, because they're important to maintaining the structure of the CSV file.
Is there a reason you'd need to keep the text delimiters in your original example?