When in creative, the vibration from a projectile originate from the player instead of the projectile's impact point. This seems to only occur when the player is within range of the wardens vibration detection range. This only seems to occur in creative, and I don't know if the difficulty affects it in any way, but it does occur on normal difficulty.
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We're tracking this issue in MCPE-153549, so this ticket is being resolved and linked as a duplicate.
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