Share your thoughts on DirectQuery for Power BI datasets and Azure Analysis Services (preview)

Hi,
I get an unexpected result when I add another source, here Excel, to an existing dataset.

In the dataset I have an article dimension to which I want to join more attributes via the Excel file. However, in the Excel table I do not have an entry for each article, which should not be a problem. When I load the Excel file into the model I have the possibility to create the relationship correctly (1:n). All good so far...

If I then use elements from the Excel file and the article dimension in the report, the contents are automatically filtered, i.e. I only get the data records for which entries are maintained in the Excel file. I would have expected a different result here and not a filtering.

If I open the "original" dataset and add the same Excel file to the model, I have the desired behavior in the report, i.e. the additional information is added to the records for which there is an attribute, if there is no attribute, the field remains empty.

I would have expected the same result when joining to the existing dataset.

Is this behavior desired or am I doing something wrong?