Doesn’t the IR involve hours spent ADF tracking?

It is true that the skill test is out of date and the ADF plays a larger role than is reasonable, given the advent of GPS and Performance-Based Navigation (PBN). However, NDB approaches are still very much needed by GA pilots worldwide, and the skills of using a single needle for tracking and for holding are still relevant.

Think of this as being a way of putting you under pressure to show that you can deliver safe basic instrument flying and competent decision making whilst being distracted.  It could be worse – you could be expected to fly while knitting a tea cosy or being hit about the head with a wet fish!