I don’t think he is making an argument that you should prefer pure formed interactive systems. Only that if designers want to design consciously, rather than randomly or intuitively, then it helps to frame those discussions in terms of well understood terminology.
I agree with this argument, since I lean towards the idea that systematic thought is more effective in abstract domains than non-systematic thought. I do think it creates a tendency to miss the gestalt qualities which make interactive systems succeed or fail, but I since this style is by far the dominant style of game design and analysis, I also think its worth taking the systematic point of view seriously.