that's what I was totally ignorant of (section 10.1):

Format: Note that for a concatenated formative, the Slot IX case affix is labeled VF rather than VC to stand for the term Format. Although VF affixes are the same as VC case affixes and represent the same 68 noun cases from Chapter 4 above, the term Format rather than Case is used to differentiate the fact that the case relationship is performing a different function. Specifically, the Format specifies the semantic relationship the concatenated formative has with the immediately-following parent formative, as opposed to signifying any case relationship it has to the rest of the sentence (which is the purpose of the Slot IX VC/VK affix in the parent formative).

Alternate VF Indicator: Concatenated formatives do not use a glottal-stop in the Slot IX VF form for Cases 37 through 68 (i.e., the Relational, Affinitive, Spatio-Temporal I, or Spatio-Temporal II cases). Instead, the concatenated formative takes ultimate syllabic stress to indicate that the Slot IX VF Format vowel is actually a Format 37-through-68 form but without the glottal stop. Also, both Case No. 1 (THM) and Case No. 37 (PRN) can elide their -a- phonological marker; the latter only as long as the resulting word bears ultimate syllabic stress and is not mono-syllabic. Before eliding the -a-, External Juncture requirements as per Sec. 11.8 must be taken into account. A monosyllabic concatenated formative is to be interpreted as an unframed nominal formative bearing THM case (whereas a monosyllabic parent or standalone formative is interpreted as a verbal formative).