Whitespace following a text declaration

Given an external parsed entity of the form:

<?xml version="1.0" encoding="UTF-8" ?>
<extEnt attr="x"><sub2>z</sub2></extEnt>

I'm surprised to discover that the parser in .NET includes the newline after
the text declaration as part of the entity's expanded text, while both
Crimson and Xerces (the versions built into JDK 1.4 and JDK 1.5
respectively) exclude the newline. 

I can't see any justification for excluding the newline: is this a
non-conformance?

Michael Kay
http://www.saxonica.com/