I have a number of Sapote trees here in Nipomo. My oldest tree is a monster, 2 ft diameter trunk. It is grafted with Pike and Vernon, bushels of fruit everywhere enhanced with fruit flies. I also have two dwarfed trees, one a Pike, one a Vernon. Both produce normal sized fruit. Each "tree" is approx 4 ft tall, and is over 15 years old. These are the same varieties in the monster tree nearby. The difference is that the C. edulis "Pike and Vernon" are grafted on yellow sapote rootstock C. tetrameria. Obviously no incompatibility with more than 15 years since grafting. One is in the ground, one in a half barrel.
Conversely, yellow sapote, c. tetrameria, grafted on c. edulis results in a semidwarfed tree, about the size of a peach tree. I have both #6 and #7 varieties of C. tetrameria grafted on white sapote, C. edulis. Each tree is approx 15 years old or more.
It seems that the size of white sapote, C. edulis, could be controlled with the use of a C. tetrameria interstem a technique used in apple dwarfing. Perhaps then, a white sapote tree would fit in the average city-sized lot.