jetpack_development_mode filter breaks Custom CSS and Extra Sidebar Widgets when working locally

We had a couple users report that the Custom CSS and Extra Sidebar Widgets modules were not working as expected for them when working locally. I was able to reproduce by following these steps:
1. Install WordPress locally.
2. Install Jetpack.
3. Enable dev mode with the `jetpack_development_mode` filter.
4. Activate Custom CSS and Extra Sidebar Widgets under Settings > Jetpack.

_Expected_: Custom CSS menu item added under Appearance, and Extra Sidebar Widgets added under Appearance > Widgets.
_Actual_: No menu item is added, and no new widgets appear.

Both users reported they were using Bitnami's WordPress stack to work locally, but I was also able to repro with a local VVV install. The issue only occurs when using the filter, and does not occur when using the dev mode constant in wp-config. So, for the time being we can suggest that as a workaround.