CTRL+Pick Block on a command block is not reliable

Using CTRL+Pick Block on a command does not consistently retain the command of the pick-blocked command block when the item is placed back down.

Steps to reproduce:
1. Place down a command block and enter a command
2. CTRL+Pick Block that command block
3. Place down the command block received in step 2 and edit the command
4. CTRL+Pick Block the command block from step 3
5. Place down the command block received in step 4
6. Observe that the command in the command block of step 5 is the same as in the very first one

Observed behavior:
The command in the third command block is the same command as in the first one; The edit has not been retained.

Expected behavior:
The command in the third command block is the same command as in the second one, with the edit having been retained.