Yeah had the same story broadly confirmed by several Motown artists I interviewed Ady.
Once I'd heard it once, I asked others so what really happened to Tammi Terrell?. Normally they said "Can you turn the tape recorder off and I'll tell you about it, but you mustn't print it". It's in none of the Motown books and all I ever read on it was poor Tammi had a brain tumour and died in Marvin's arms etc etc.
Not true if these stories about David's role are accurate, and they crop up too frequently not to hold any water.
Also heard some nice little corkers about BG, Little Willie John, Diana R etc....but couldn't possibly repeat those either.