Currently, when trying to create a timeseries collection on a system collection, say system.users, the creation will fail. However, it will leave behind the buckets collection, because the command fails when creating the view, with an error that reads:

View name cannot start with 'system.', which is reserved for system namespaces

The buckets collection in this example would be named "system.buckets.system.users", which is an invalid namespace name, and would cause problems down the road with commands such as movePrimary.