The 'before' and 'after' is what update_landuse_labels() is supposed to do. The labels that come out of the farmer are too long and this routine assigns new unique labels which. It is just important that the changes of the labels are consistent throughout the files.
The diagnostics output however is something that I have to look into. If you only have a initial plant growth but no management operations (I assume this is the case for forest land uses) then there should not be a label for a forest management in the landuse.lum.
I will fix that. Thanks for taking apart the farmr so throroughly 😄