comments and pi inside simple content

In 3.1.4 of Structures, it states that comments and pi are ignored
when constructing the content of an element.  This does not appear
to depend on whether the content is simple or complex.  Thus

     <number>1<!-- this is a comment -->2</number>

is the same as <number>12</number> for purposes of validation.

This seems rather counter-intuitive.  It also conflicts with the
way xslt and other xml processors handle content - they would
treat the "1" and the "2" as separate text items.

Do I correctly understand the document, or did I miss something ?