Minecart behaviour is different compared to 1.21.1 even when the "Minecarts Improvements" experiment is not enabled. I'm assuming this is unintended because it was not mentioned anywhere in any changelogs.
This bug negatively affects some sensitive redstone contraptions using minecarts made by the technical minecraft community.

Steps to reproduce

• Download the attached world and open it in 1.21.1 or build the setup shown in the attached screenshot.
• Flick the lever so that the dispenser spawns a minecart.
• Observe how the minecart doesn't get destroyed by the lava cauldron.
• Now open the world in 1.21.2-rc1 and repeat the previous steps.
• Observe how the minecart ends up getting destroyed by the lava cauldron.