The CUBE Revit plugin allows you to directly open models hosted on the CUBE app in Revit, make changes, and publish them. These published files can be downloaded into your local system.
To host models on the CUBE app in Revit follow these steps:
Select the Space and the File that needs to be downloaded to Revit.

File gets downloaded to Revit

Make your changes and click Upload. If any 3D view contains 2D elements or referenced CAD, the plugin asks whether to clean it up before publishing (see Auto cleanup of CAD in 3D views below).

When you publish (upload) a model to CUBE from the Revit plugin, the plugin can detect and auto-clean referenced CAD from the file's 3D views, so the model displays cleanly on the CUBE web app.
If no 3D view contains 2D elements or referenced CAD, publishing goes ahead as normal with no prompt.
Removing stray CAD from 3D views before publishing produces a cleaner model and a better viewing experience on the CUBE web app.
My upload was cancelled after I clicked No on the cleanup prompt.
This is expected. Choosing No aborts the publish so you can clean up the CAD manually in Revit, then publish again.
The cleanup prompt didn't appear.