> XSLT 2.0 and XQuery 1.0 Serialization hints there is more. It 
> says "Specifically, CR, NEL and LINE SE ...". Note the use of 
> the word "specifically". 

You seem to be reading "specifically" as meaning "for example". That's not
my reading. "For example" carries a strong hint that what follows is
incomplete; "specifically" merely states that what follows is more specific
than what comes before. "Specific" doesn't mean incomplete, it means
precise.

In this case the first sentence says "certain characters must be escaped",
which invites the reader to ask "which characters?" and the second sentence
answers the implied question. "Specifically" here is merely a connector
between the two sentences, the first sentence stating the rule in general
terms and the second stating the same rule in more specific terms.

It's probably true that the authors of this paragraph were hedging their
bets: stating the general rule first means that if implementors discover
additional characters that need to be escaped in order to achieve
round-tripping, they have clear guidance on what to do. But it also reads to
me as if they were trying their best to provide a complete list.

Michael Kay