Trying to destroy File Vault encryption key once Sleep mode kicks in

I've just enabled File Vault in OS X 10.10 and I understand that this protects the drive when the system is shut down but a vulnerability remains when the system is in sleep or standby/hibernate mode (as the encryption key remains in RAM until the system is shut down). After some research, it appears that the following command combination in Terminal is supposed to 1) destroy the key once the system goes into standby/hibernate mode, and 2) shorten the sleep state time before the system moves to standby/hibernate mode to only 10 seconds:

sudo pmset -a destroyfvkeyonstandby 1

sudo pmset a- standbydelay 10

However, after doing this, rebooting and testing, I'm not seeing any evidence this is working as desired. When I run this command:

pmset -g

Terminal shows "DestroyFVKeyOnStandby 1" and "Standbydelay 10," which seems to indicate the desired settings are in place. However, when I put the system in sleep mode, wait a few minutes and power it back up, I'm not getting a separate File Vault PW requirement (just my standard user PW required input) and I'm not seeing any delay at all in returning to awake status (I understand that the decryption process should introduce a delay).

I'm not sure if Yosemite has rendered these commands obsolete or if I'm missing something else. Can anyone help? Thanks much.