The bad news: I don't think this is going to be fixed. I can't give any more details because I'm under NDA. Sorry.
The good news: I found a workaround that automatically ejects (and spins down!) the external drives before sleeping, and automatically remounts them when waking.
The bad news: You need to be somewhat comfortable in Terminal to set it up.
You need to install and run the Sleepwatcher daemon which can trigger events on sleep/wake. Visit this page and follow the instructions up to the point where it says
"At this point, you’ve successfully installed SleepWatcher. And if you are planning to use method 3, WAIT! There’s one more thing to do before moving on."
AND THEN STOP becuase the rest of their instructions will cause your eternal drives to unmount instead of eject (which will cause them to keep spinning instead of spinning down).
Instead, you need to follow these instructions.
Open Terminal and type:
diskutil list
Each disk will have a unique identifier that will look like this:
disk1
disk2
disk3
etc.
In addition, each disk's volume will also have its own unique identifier, like this
disk1s1
disk1s2
disk2s1
disk2s3
disk2s4
disk3s1
etc.
Now you need to open TextEdit. Ensure the TextEdit document is set to plain text and not to a rich text (if a Make Plain Text item appears in the Format menu, select it.)
You need to figure out the identifier for each of the disks and make a text file that looks like this:
#!/bin/sh
diskutil eject disk1
diskutil eject disk2
diskutil eject disk3
That's what mine looks like. The above commands eject each disk and make it spin down. These commands will be run when you sleep your Mac. Save this file to the Desktop for now with the filename "sleep.txt".
Then you need to find out the identifier for each volume and make a text file that looks like this:
#!/bin/sh
sleep 5
diskutil mount disk1s2
diskutil mount disk2s2
diskutil mount disk2s4
diskutil mount disk3s2
diskutil mount disk3s3
That's what mine looks like. Each identifier corresponds to a different volume on my external hard drives. Each command above will reattach the volume. These commands will run when you wake your Mac up. Save this file to the Desktop for now with the filename "wakeup.txt".
You now need to set the proper permissions on the above files and move them into the right places. This also requires Terminal. Copy and paste the following commands into Terminal:
cd ~/Desktop
chmod 755 sleep.txt
chmod 755 wakeup.txt
mv sleep.txt ~/.sleep
mv wakeup.txt ~/.wakeup
cd ~
sudo chown root .sleep (you will have to enter your password and press return when prompted)
sudo chown root .wakeup
After this your external drives should eject and spin down when sleeping, and spin back up and mount when waking.
