When creating a new top level collection you have the option to specify the collection type.

It is not required which I believe is OK. However the options should be mutually exclusive. It doesn't make sense to have Data Collection (Geophysical Dataset) that is also a Model Source Code dataset.

This is currently a pretty significant shortcoming in the domain model design Until that is better resolved the user interface should better prevent invalid combinations.

The terminology isn't consistent. You create a 'Data collection', however on the dataset page that triggers the Geophysical tab.