Update: I just discovered that the device wakes up again because the power saving timeout I set works both ways (wake up to standby and standby to wake up).
I think this may be a bug. Disabling that feature for now and re-enabling my wake.py and standby.py scripts for further testing.
EDIT: I can confirm that. Now the device correctly goes into suspend mode and stays that way, and the NAS puts the disks to sleep 
@sam_nazarko could it be a bug?
UPDATE 2 (sorry, today I have time to work on this since I’m stuck at home):
Clarification: I’m using the picture slideshow screensaver and the screenshot folder is mounted via autofs/nfs on the NAS.
Earlier I put the Vero in suspend mode before the screensaver kicked in. All was good and after a while the disks went to sleep.
Now I tried to put it in suspend mode after the screensaver kicked in. I can see from the logs that it’s still pulling images from the NAS.
In both cases, CPU usage of kodi.bin was pretty high during standby.
I hope I can help debug this.