I haven't tested in any other versions of Minecraft just 1.16.2 so I created a new world in 1.16.2 to like mess around and stuff when I went to the end I killed the ender dragon using /kill @e[type=minecraft:ender_dragon] it killed 9 entities It should just be 1 since there's only 1 ender dragon so that's kinda strange this actually might relate to MC-105770 but I have no clue.
To reproduce:
Create a new single-player world with cheats and with creative mode then make an end portal when you get to the end just make sure like all the chunks all loaded for the ender dragon then kill it with /kill @e[type=minecraft:ender_dragon] then it should say 9 entities.
Thank you for your report!
However, we are already tracking this issue, and this report is a Duplicate of MC-146503, which has been marked as Won't Fix - while this behaviour is not desirable, the developers have said that they will not or cannot fix it.
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