Shall meta higher-priority stream 'cover' a lower-priority one?

[mstanki-ra]

In my home multiroom setup with homeassistant I have set up Snapcast with three sources and two Mopdy instances (Docker images): one for music, one for announcements (doorbell, etc) and one meta merging both of them (see config below).

I have two Snapcast clients playing the meta stream.
When my HA automation plays a doorbell it waits until I stop my music mopidy and then plays the sound. Is this normal? -I expected to mute temporarily the music while playing bell or blend both sounds.
Announcement stream is set as first in the meta stream to have highest priority.

Snapserver.conf

[stream]
stream = tcp://0.0.0.0?name=Snapserver
stream = tcp://0.0.0.0:4954?name=Announcements
stream = meta:///Announcements/Snapserver?name=All

[http]
doc_root = /usr/share/snapserver/snapweb

Announcement Mopidy config excerpt:

[audio]
output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! wavenc ! tcpclientsink host=announce>

Music Mopidy config excerpt:

[audio]
# Comment out this line for mopidy to use the default audio device
output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! wavenc ! tcpclientsink host=snapserv>