I think the May 21, 2008 memo should have included a reference to page 111 of the Interpretations
Just a thought
USSF answer (December 17, 2008):
1. When the May 21 2008 Memo on official changes in the Laws of the Game was prepared and published, the current year’s Lawbook was not available and so we could not know what the Interpretations would say on any topic, much less this one.
2. When we were ready to prepare and publish the supplemental memorandum, we reviewed the Lawbook (including the Interpretations section) closely to identify those areas where IFAB had changed the language enough that the “clarification” appeared to modify our current understanding and implementation of the topic. The topic of the “pass back to the keeper” was not one of them. Nothing appeared in the Lawbook (or the Interpretations section) that significantly altered any of our earlier memos on this topic or what is plainly stated in Advice to Referees.