This minecart renamed as "@" only drops if the command block minecart is spawned using a spawn egg and broken in Creative Mode. It does not drop if the command block minecart is spawned by a spawner, spawned with /summon, or broken in Survival Mode.
Use this command and try it out:
/give @p bee_spawn_egg{EntityTag:{id:"minecraft:command_block_minecart"}}
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Thank you for your report!
However, we are already tracking this issue, and this report is a Duplicate of MC-41893, which is a report that has not been resolved yet.
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