RootVehicle detection no longer works as it used to

The following command, executed in a repeat command block under a detector rail to kill the nearest minecart if there is no player riding a minecart nearby, does not work. Used to work in 1.20.4. I tried killing the minecart without any condition and it does work, so I deduce that the problem is in RootVehicle detection or a change in syntax that I am not aware of. Searched through the changelogs but could not find anything I deemed to be related.

execute unless entity @p[distance=..3,nbt={RootVehicle:{Entity:{id:"minecraft:minecart"}}}] run kill @e[distance=..3,type=minecraft:minecart,sort=nearest]