When a player rides a mob, the player's model moves as needed. But if you dismount the player and mount him on the mob, then the player will be in the real position of the entity, and not in the position of the model with interpolation. In the video, I showed two cases: 1) without teleporting the player (the player does not dismount). 2) the player is constantly rotated by the command by 1 degree around the Y axis and mount on the mob.
(Sorry for my English)
Commands:
load
kill @e[type=minecraft:rabbit,tag=v]
summon minecraft:rabbit ~ ~1.5 ~ {NoAI:1b,Tags:["v"]}tick
execute as @e[type=minecraft:rabbit,tag=v,limit=1] at @s run tp ~-0.5 ~ ~
execute as @a[tag=r] at @s run tp @s ~ ~ ~ ~1 ~
execute as @a[tag=r] at @s run ride @s mount @e[type=minecraft:rabbit,tag=v,limit=1]
I think the issue as described does not happen. The player does always line up with their mount. It's only with the repeated dismounting and remounting that an, in my opinion, expected desync occurs