Flattening is incomplete with Maven 3.9.0 split repository

[GethDeeo]

Hi,

I've started using the Split Local Repository feature, and noticed that flatten-maven-plugin now spews lines similar to this:

[WARNING] The POM for <artifactN> is missing, no dependency information available

Of course, the flattened POMs reflect this (e.g. missing dependency exclusions) 😢

Edit: This only happens, when flatten.dependency.mode is set to all.

Additional information:
Maven 3.9.9
org.codehaus.mojo:flatten-maven-plugin:1.6.0
aether.enhancedLocalRepository.split=true
aether.enhancedLocalRepository.splitLocal=true
aether.enhancedLocalRepository.splitRemote=true
flatten.dependency.mode=all

Slightly related issue: #339

Is there any workaround?