Deltas are the difference between morphed and original X Y Z vertices.
Deltas are stores as a table
index dx dy dz
index dx dy dz
........................
Where indez is the vertice number of the body or prop part and dx = xmorphed - x original.
Index is a long integer and dx, dy,dz are floating point numbers.
If dx and dy and dz becomes too small, near zero or zero dx, dy,dz are not stored in the table
You can clean and optimize a morph target removing useless deltas that are too small.

Stupidity also evolves!