In the documentation it says

bool ofDirectory::createDirectory(const filesystem::path &dirPath, bool bRelativeToData=true, bool recursive=false)

Returns: true if directory was created successfully

However when I look in the code it will always return true:

bool ofDirectory::createDirectory(const std::filesystem::path& _dirPath, bool bRelativeToData, bool recursive){
	auto dirPath = _dirPath;

	if(bRelativeToData){
		dirPath = ofToDataPath(dirPath);
	}
	
	// on OSX,std::filesystem::create_directories seems to return false *if* the path has folders that already exist
	// and true if it doesn't
	// so to avoid unnecessary warnings on OSX, we check if it exists here:
	
	bool bDoesExistAlready = ofDirectory::doesDirectoryExist(dirPath,false);
	
	if (!bDoesExistAlready){
		
		bool success = false;
		try{
			if(!recursive){
				success = std::filesystem::create_directory(dirPath);
			}else{
				success = std::filesystem::create_directories(dirPath);
			}
		} catch(std::exception & except){
			ofLogError("ofDirectory") << "createDirectory(): couldn't create directory \"" << dirPath << "\": " << except.what();
			return false;
		}
		return success;
	}
	
	// no need to create it - it already exists.
	return true;
}

Basically when read as bDoesExistAlready is true the return value should be false.

However this gets tricky if the creation of the directory fails, it will then also return false which would then have different meaning.