Yes absolutely true.
If you replace the background shader in the background object with this default shader below, then you also get a nice subtle effect without noise and without a performance hit.
It's basically the bluesky colour from the atmosphere node pasted into the luminosity and brightness (HSB) lowered from 100 to 50.
You can choose to use HSB brightness for control or link a constant scalar to the luminosity function input, so that you can access it from the main node network (my preferred method, I hate stuffing everything inside nodes).
You know these tricks, I know, but in case someone else might not...
<terragen_clip>
<default_shader
name = "Default shader 01"
gui_use_node_pos = "1"
gui_node_pos = "80 -160 0"
gui_group = ""
enable = "1"
input_node = ""
gui_use_preview_patch_size = "0"
gui_preview_patch_size = "1000 1000"
diffuse_colour = "0 0 0"
colour_image = ""
colour_function = ""
translucency = "0 0 0"
translucency_image = ""
translucency_function = ""
luminosity = "0.0461499989 0.09869000316 0.2158000022"
luminosity_image = ""
luminosity_function = ""
specular_roughness = "0.8"
specular_roughness_image = ""
invert_specular_roughness_image = "0"
convert_specular_roughness_image_to_linear = "0"
specular_roughness_function = ""
specular_roughness_model = "3"
metalness = "0"
metalness_image = ""
convert_metalness_image_to_linear = "0"
metalness_function = ""
reflectivity = "0.75 0.75 0.75"
reflectivity_image = ""
reflectivity_function = ""
reflection_tint = "1 1 1"
index_of_refraction = "1.5"
displacement_direction = "1"
displacement_multiplier = "0.01"
displacement_image = ""
convert_displacement_image_to_linear = "0"
displacement_function = ""
displacement_offset = "0"
opacity = "1 1 1"
opacity_image = ""
use_alpha_channel = "0"
invert_opacity_image = "0"
opacity_function = ""
alpha_from_colour = "0"
alpha_key = "0 0 0"
key_tolerance = "0.1"
image_projection = "4"
projection_camera = ""
unpremultiply_colour = "0"
unpremultiply_metalness = "0"
unpremultiply_translucency = "0"
unpremultiply_luminosity = "0"
unpremultiply_reflectivity = "0"
unpremultiply_specular_roughness = "0"
>
</default_shader>
</terragen_clip>