This is not a duplicate of MC-193083
That bug report explicitly mentions dismounting mobs not minecarts.
And yes there is a difference between the two because converting mobs used to not dismount minecarts until 24w36a
So this can't be a duplicate since this issue didn't exist back then.
Note 1: Mobs only dismount boats for a single tick, and then remount them, so it's best to test this with minecarts.
Note 2: This is a TMC sensitive issues. Several contraptions rely on mobs converting while being in minecarts.
Steps to reproduce
Load version 24w35a
Put a piglin inside a minecart in the overworld
Wait for it to convert
Repeat the steps in 24w36a
Observed Results
In 24w35a the piglin stays inside the minecart upon zombification
In 24w36a the piglin dismounts the minecart (and falls though the floor)
Expected Results
Mobs would stay mounted inside minecarts after converting to another mob. (Confirmed by MC-163767)
Note 3: If you want to test villager zombification/curing go to 24w37a since in 36a they just die.
Can confirm.