VC:Standalone Document Declaration

Hi,

XML spec states following VC:Standalone Document Declaration:
"The standalone document declaration MUST have the value "no" if any external markup declarations contain declarations of:
....

element types with element content, if white space occurs directly within any instance of those types."

but why so many tools don't report such error? Did I misunderstood the statement?

sample xml document:

<?xml version='1.0' standalone='yes' ?>
<!DOCTYPE animal SYSTEM "ibm32i04.dtd" [
<!ATTLIST animal xml:space (default|preserve) 'preserve'>
]>
<!-- This is against VC: Standalone Document Declaration in P32
The standalone document declaration has the value "yes", there is an 
external markup declaration of element with a element only content type, and 
white space occurs directly within the mixed content.
-->
<animal><a>This is a 

yellow tiger</a> <b/>
<c/>

</animal> 


Thanks for any help.

Stephen Suen