Modern versions of Sparkle are a less random in when to show the update alert (lots of software, iTerm including, use ancient versions of Sparkle)
DND is not properly/reliably detectable for 3rd parties. Support for Notification Center is not well designed for a framework to control and works as an auxiliary/supplemental (not primary) functionality for 3rd parties, so apps themselves would have to opt into using it along with adding a lightweight UI indicator which may need to be tailored to the app in question.
