They're not tapered rollers though.
What are they in fact.
Angular contact ball bearings ?
The adjustments on the steering head stem on many a british bike are quite substantial,
none of these slender little adjustment rings.
I'd suggest these above are too wimpy to serve as adjustments for a taper roller bearing in fact,
you'd have quite a high loading on just a few skimpy threads.
Even if the adjustment rings were made of kryptonite.
A slimline featherbed top stem and adjustment nut.
There is an inch of fine threaded nut there (and under the bearing inner).
Pardon the gunge in the thread, it pays to keep such things greased.
There is another large nut that clamps down on the top of this, to lock it.
Also with a fair old threaded length.
Overkill ? Or fail safe ...
The more you read on this, the bigger the dogs breakfast of facts, opinions and just plain blather ??
"We demand rigidly defined areas of uncertainty" ...