When updating a static file (e.g. a .css file) in a web application bundle, the static file is just updated on disk without restarting the entire bundle. However, if the .css file lives in a regular bundle, the entire bundle will be restarted. So, this new feature request is about extending support for static file updates without a restart to regular (non-WAB) bundles.
This probably will require server & GEP changes.