Not all information from parent available in plugin?

In a multimodule project, it seems that not all information of the parent project is passed (or otherwise available) in the assembly plugin.

Given the attached minimalist setup, I echo the project.parent.name / version and project.name / version.
During mvn assembly:assembly it seems the project.parent.name variable is not available, while the version is.
Output:
[echo] Outputting some variables
[echo] `-> project.parent: ${project.parent.name} - 1.0-SNAPSHOT
[echo] `-> project: Module Name - 0.5-SNAPSHOT

Instead of the expected:
[echo] Outputting some variables
[echo] `-> project.parent: Project Name - 1.0-SNAPSHOT
[echo] `-> project: Module Name - 0.5-SNAPSHOT