Yes, keep Spectrum Music separate because it was previously a label under PolyGram ownership, and so became a Universal property when that company bought PolyGram in 1998/99. I can't imagine that there would have been a copyright problem on the two missing tracks, as Motown always owned the recordings and Jobete/EMI owned the publishing. Maybe something was wrong with the master tapes.
I've added Universal as a secondary label, as should be the case with most Spectrum CDs, as having had a look at CDs in their catalogue, they have a number of issues from other label's music (tie-ins)...
...If it is simply kept as Spectrum for all of these as primary, they will all appear on the spectrum page together, but if a joint label is made, they will be regarded by the system as a different label, and so won't appear in Spectrum listings.
(I'll amend the Spectrum / Universal label too phil)
It looks like UK buyers got slightly short-changed with this collection as the US and European releases of this some ten years previously had included two additional tracks ... "Why Do You Want To Let Me Go" by Marv Johnson and "I Wouldn't Change The Man He Is" by Blinky.