You have to restart a slave’s slave to pickup Pool/Group assignment. Otherwise it just sits there and won’t find a job.
To me, it seems like it just takes a reaaaaally long time for them to notice they should be in a different pool/group.
Admittedly ‘never’ for me was “5 minutes until I restarted them.” 
Currently, the slaves are set to invalidate and reload their slave settings (which includes the pools and groups) every 5 minutes. Can you double check on your end if your slaves recognize the changes after waiting at most 5 minutes?
Yeah took about 3 minutes to pick it up and then finally start. Maybe there could be a dirty bit or something in the database for slave settings to trigger a check?
Thanks for checking this. We can probably look at changing how this works in the future, or later in the beta cycle if we have time.
Cheers,
- Ryan