(I would attach an image but Jira wouldn't let me)
Using this command in a command block:

/summon minecart ~ ~ ~2 {NoGravity:0b,Glowing:0b,Invulnerable:0b,CustomNameVisible:0b,Rotation:[-90F,0F],CustomName:'[{"text":"1","color":"red","bold":true,"italic":false},{"text":"2","color":"#FF8000","bold":true},{"text":"3","color":"green","bold":true},{"text":".data=minecart","color":"reset"}]'}

I summoned a minecart...
But the hitbox was above the minecart!
But when the minecart went off some tracks,
The hitbox was fixed!

This may be something to do with my world but:
-No data packs
-Minecraft version 1.16.4 (No mods)

(I'm using the command to give a minecart data so I can build a launch system)