I've got the exact same issue with the default-python template (CLI v0.242.0).  I've made no changes to the generated output but no src files are uploaded.  If I upload them manually via the UI, the sample Job runs.

I even tried syncing directly via a few variants of:

databricks sync . /Workspace/Users/me/.bundle/backup_automation/dev/files/src/ --full --debug

and no files were uploaded and I saw no useful messages in the log.