Feature Model not constructed as expected.

[tabris87]

I used the SPLOT feature model generator desktop version and used a configuration as follows:

• 20 features
• 30% mandatory features
• 0% optional features
• 70% alternative features
• 0% exclusive features

Min. Branching Factor 20
Max. Branching Factor 20
Max. Size for feature groups 20

No Cross Tree Constraints, and therefore no clause density.
And the model consistency was set to "Consistens Models only".

During checking the Feature models i got feature models with only 1 or even no mandatory features.
Is this a wanted behavior?
Because, for me it looks like a bug.