Sounds very Linear to me. Even if he’s going crazy with mental tangents, you describe them as ‘lines’ of thought - endless chain-links of “if this happens, then this will happen, and this, and this…” etc etc. It’s all linear cause-and-effect.
If Linear thinkers are all about ‘lines’ of thought, then Holistic thinkers are about volumetric space. They have many things to maintain simultaneously in order to achieve a certain balance or imbalance. Push and pull, ebb and flow, status-quo vs not status quo, etc.
Basically Linear thinkers find a path and follow it - Holistic thinkers find a space and tend to it.