I have two reasons I want to "know" countersteering:
1) if you know you're doing it, you can do it better; and
2) Riders that don't "know" they're doing it, frequently think they're doing it some other way- leaning their body into a turn (coincidentally pressing the correct bar) for example. When there's an obstacle to avoid, then they panic and try to steer to avoid an obstacle. The result is... not pretty.
As an instructor, I don't care which theory students believe makes countersteering work, or whether they believe any of them. They can believe there are gears in the steering head that are part of a CIA plot to keep terrorists off motorcycles if you want- just believe "press left, go left; press right, go right".