This is not parametric design, this is algorithmic or generative design. In the edition of the process is the paradigmatic change, parameters are at an interface level, the data is the current, not the field. So if you want to learn about processes, you must learn the language that can produces them. If you learn a language, express yourself with it. You learn in a genuine way only if you face your own problems/exercises. If you want to learn quickly and less deeply, then books or teachers are your best choice. But I do not think there is a logic behind this, if there is one, it is very generalist or partial. There can be no an instruction to make art with instructions. There are logics of all kinds, although grasshopper is very limited in this because it is sequential (non-parallel), in cascade (it is difficult to control the flow) and acyclic (no plugins, no loops). But it allows you to code within it :)

Btw, You have asked a general question in a particular group, on the main page you have an +Add a Discussion in the forum panel to ask general questions.