In brief
The eggplant can be prepared whole for a soft inside or cut into cubes. The two methods lead to different dishes.
Useful to know
For a soft inside to scoop out, the university guide suggests cutting the whole eggplant slightly to the side and baking it until soft. After cooling, it is cut and the inside is separated. Another option is slicing; the skin is edible. [1]
When purchased, it looks for a hard, shiny eggplant, heavy for its size and without crust ruptures. Rinse before cooking. [1]
The choice between the two methods starts with the final dish. For an appetizer, the separation of the soft interior is logical. For a mixture of roasted vegetables, the cubes give another way of distributing. These are not interchangeable instructions with the same final appearance.
Don't add a universal step just out of habit. If the recipe does not require peeling, you do not have to assume that the skin must necessarily be discarded. Follow the specific purpose and check the softness of the real product.
Sources
For further detail and to check the information: