Well, we'll know for sure once Mobil gets back to us. I can't see why they'd change that figure unless it actually changed, they wouldn't need to touch it to adjust for SP.
On the low VII thing, Mobil has an extremely low VII (2.6%) 0w-20 in one of their blending guide examples:
View attachment 93242
Which I calculated as having a BOV KV100 of 5.38cSt based on the properties of SpectraSyn 6 and 4 (5.8cSt, 4.1cSt) and Esterex NP343 (4.3cSt) using the Widman calc. Interesting how, despite how close that oil is to the EP 0w-20 you have on your spreadsheet, VII content is shown above as being 1/2 what you've calculated. I suspect this may come down to VII type assumptions one is forced to make when making a calculator that covers such a broad range of products.
While SpectraSyn 8 would fail the CCS test at -35C (it's 4,800cP @ -30C, so would be about 9,600cP at -35C) we can see SpectraSyn 6 works (2,260cP @ -30C; ~4,520cP -35C) so I suspect it is quite possible to meet the target with a heavier base oil blend. If they are blending in some of the Synnestic AN's, that'll also negatively impact the VI, since they are quite low (Synnestic 5 is 65). My suspicion is that, if they confirm the PDS is accurate, we are seeing the artifact of a predominantly PAO and AN blend with a splash of VII to bump it up to 8.6. If the BOV was around 7cSt @ 100C, VII content would be basically negligible, acting basically likely a monograde, but wouldn't actually be one due to that splash of VII.