Separate TTS toggle for bedtime vs alarm would be perfect and skipping bedtime notification entirely when DND is on if not using sleep tracking makes total sense.
Hoping this lands soon thanks for pushing it
Each notification can have a different behavior which you can configure in the system settings > Apps > Sleep > Notification. You can configure the Bedtime notification not to override DND.
In the new version, with the Priority mode for DND, the TTS Bedtime is not read.