• they don’t like it if you run spacers above the stem

    Because you're supposed to use their heavy duty flanged expander/reinforcing plug in a very specific position relative to the stem clamp.
    They could avoid the issue by making the steerer from a bit more material, but adding 50g to the fork wouldn't look so good in their marketing material, so they make the fork too light and then void your warranty if you fail to use their 50g plug

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