A genuine question why do I need one on top
The connection of the stem to the steerer is much more secure if the steerer projects slightly through the stem clamp, rather than stopping short of the top of the stem. You then need a spacer on top to let the preload adjuster work.
@gbj_tester started
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The connection of the stem to the steerer is much more secure if the steerer projects slightly through the stem clamp, rather than stopping short of the top of the stem. You then need a spacer on top to let the preload adjuster work.