The transit lanes are arbitrary lines of convenience on a map. The actual available deep water is considerably wider.So you're saying that a fully-loaded supertanker can pick his own transit lane if the need be? I'm thinking that there are limits to how far away from the center it can safely transit. Within reason, of course.
Sure there are limits-whatever depth of water that will support a ship's draft. And that available depth is much wider than the Traffic Separation Schemes themselves. The TSS is there more to prevent collisions than groundings.
Here is the chart of the straits. Larger scale here.