Curious, indeed. Universal owns both A & M and Motown, and all the Motown tracks are shown as being licensed from Universal, but not all the A & M tracks are. I suspect that they either couldn't find the tapes for some tracks, or couldn't find the paperwork to prove (or otherwise) their ownership of them. I have heard that for the latter situation, Universal usually aren't prepared to license the tracks out, and the company using them assumes the risk of possible future legal action if someone should turn up later claiming ownership and royalties.
Curious little collection this, covering repertoire from three different labels, including their 1968 single on ManChild, which presumably is the reason for the cryptic note on the back cover of the booklet where they admit to not knowing who owns some of the tracks (I think Motown and A&M were still in the phonebook in 2006).
There is an interesting essay on Sisters Love in the 8 page inlay/booklet as well, though there is no indication of who wrote it!