Hi Pauline,
Section 5.4.12 provides flexibility for those sponsors who wish to keep the follow-up documentation separate; they may not have the ability to use sub-artifacts to help specifically search for follow-up records. If section 5.4.12 was removed, sponsors who adopt the Reference Model would then be forced to file follow-up documentation in the same location as the original monitoring visit records (section 5.4.3) and may be more difficult to locate without the use of sub-artifacts.
Kind regards,
Eldin.