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.