When a branch is deleted, the workflow is unscheduled.
If Only build pull requests option is set to On and additional "default" branches are enabled via regex to include branches like feature-
and epic-
, many branches will be deleted. The additional red workflow is unscheduled email is alarming for customers in this case when many branches could be deleted and thus unscheduled a day.
Note: Even if Only Build PRs is enabled, CircleCI will still build all commits from your project’s default branch and tags - undocumented but in use scenario by customers is adding a regex branch setting to add multiple branches as default.