I’ll give a slightly different take on it. The brooder needs to remain dry. A wet brooder is a dangerous brooder. A wet brooder can breed disease. Poop can start to stink. Air quality may not be real good because it can contain ammonia from the wet poop breaking down. There is nothing good about a wet brooder. I would not want to go above barely damp and even that worries me some
What is your purpose of using compost or humus in there? What do you hope to gain? The mix needs to be at least damp for the organisms that beak down poop to grow and do their job.
A broody hen will raise her chicks on dirt and they will thrive. But shenormally uses a large amount of area. With chicks confined to a brooder, the poop concentration is likely to get high enough to cause a problem, where with a broody the chicks are probably pooping over a much bigger area.
If you keep it dry and keep the poop from getting too concentrated it should work, but I’m not sure what you hope to gain. Maybe we could answer better if we knew what your goal is.