mobs dont spawn in minecarts when summened by a spawn egg

I played around with some weird minecraft mechanics and I stumbled oppon this bug. I tried putting mobs in different spawn eggs->

/give @p enderman_spawn_egg{EntityTag:{id:"minecraft:lightning_bolt"}} 1

this basically gives you an enderman spawn egg that spawns a minecart when used. next I tried putting a pig in a minecart IN a spawn egg ->

/give @p enderman_spawn_egg{EntityTag:{id:"minecraft:minecart",NoGravity:1b,Passengers:[

{id:pig}

]}} 1

sadly, somehow didnt seem to work, I think this is a bug but I dont know 100% for sure...

thanks for reading and have a nice day