Question about RDFa processing rule 8 (@typeof)

Dear RDFa WG members,

  I have a question about processing rule 8 from the latest draft (http://www.w3.org/TR/2010/WD-rdfa-core-20100803/), which says:

> If in any of the previous steps a new subject was set to a non-null value, it is now used to provide a subject for type values;
> One or more 'types' for the new subject can be set by using @typeof. If present, the attribute must contain one or more URIs …
> 
> …
> 
> Note that none of this block is executed if there is no new subject value, i.e., new subject remains null. 

But aren't the initial remark ("if … a new subject was set to a non-null value") and the last remark ("none of this block is executed if there is no new subject value") a bit redundant?  Processing rules 6 and 7 either determine a new subject e.g. from @about, or, if there is @typeof, they create a bnode.  Therefore it seems to me that the precondition of rule 8 is always satisfied, and rule 8 could be simplified to:

> If @typeof is present, the attribute must contain one or more URIs …

Or is there some catch that I am overlooking?

Cheers, and thanks for any help,

Christoph

-- 
Christoph Lange, Jacobs Univ. Bremen, http://kwarc.info/clange, Skype duke4701