When exporting to Sketchup content of blocks gets correctly assigned to the corresponding layer, however the containing blocks go to “Untagged” layer in Sketchup.
@ShynnSup thanks for the link. I’m discussing this with @tim who just committed the change for the issue linked above. I will need to get hold of a more capable version of Sketchup to fully understand and test what you need though. The online version does not support layers it seems.