Imagine two large structures made of legos, say a man-figure and a car-figure. How easy would it be to snap those together, to make a "man in a race car" figure

Imagine two large structures made of legos, say a man-figure and a car-figure. How easy would it be to snap those together, to make a "man in a race car" figure? A moments thought would show it would be quite hard. Neither is likely to have merely a flat surface. So basically, increased complexity of components, any components, makes them harder to combine - except in very carefully controlled circumstances.