When you use /teleport command to any entity except player their motion is reset just like when we have problem with /tp and player before
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However, this issue is a Duplicate of MC-104494.
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If I recall correctly (and as shown by that duplicate) this was in issue in previous versions too; the smooth relative teleport logic was only ever applied to players (as only players actually have a need to be smoothly teleported from their point of view).
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