Setting either of the screensavers to "None" (When Playing or When Stopped) seems to be permanent.  Even after changing the setting to something else, digital clock for example, the screensaver action remains "None".  This also persists across both screensavers.  So setting None in When Stopped carries over to None in When Playing as well.
I tested this using a delay of 10 seconds for the screensaver activation to make things easier to validate.  I have not tested this using different delays.

This also happens on Baby Boom, I have not checked other devices.

Steps to repro:

1. Set screensaver delay to 10 seconds
2. Set When Stopped screensaver to Digital Clock
3. Ensure music is stopped and wait for screensaver, verify digital clock appears
4. Set When Stopped screensaver to None
5. Wait 10 seconds and verify screen dims but no screensaver activates
6. Set When Stopped screen saver to digital clock (or any other setting)
7. Wait 10 seconds for screensaver activation
Expected:  At 10 seconds the digital clock screensaver should activate
Actual:  At 10 seconds the screen dims and no screensaver activates

8. Set When Playing screen saver to digital clock
9. Play music and wait 10 seconds
Expected:  At 10 seconds the digital clock screensaver should activate
Actual:  At 10 seconds the screen dims and no screensaver activates