With regard to grafting C. edulis on C. tetrameria or visa versa, there is no incompatibility. I have 15 year old C. tetrameria grafted on C. edulis and the tree produces prolifically normal sized fruit. The tree is about half the size of C. tetrameria on its own roots. C. tetrameria is not a huge tree like C. edulis (about size of a peach tree).
However, grafting C. edulis on C. tetrameria (white sapote on yellow or wooly leaved sapote) leads to extreme dwarfing. I have Pike and Vernon grafted on C. tetrameria rootstock and 15 year old trees are no bigger than 3 ft tall . One is still in 5 gallon pot, other in the ground. Both are same size. Production is limited by size of tree, but normal sized fruit. Each produces 3-5 fruits.
Crfg years ago did a taste test of the yellow sapote (wooly leaved sapote, C. tetrameria) and labeled two as worth propagation. These were identified as #6 and #7. Taste is different than C. edulis, color is yellowish inside, seeds are much smaller. Indeed the underside of the leaves are very fuzzy (wooly), C. edulis is smooth, except Suebelle has a slight fuzz as possible indication of mixed heritage.