The operators I'm aware of over twenty years have had no restriction on shades, 320 or 330. There are restrictions on the table depending on serial number - later 330s with EFB in table are certified stored or un-stowed (they must be latched) as I understand it.
I would say that on some of the older CRT screens, in bright sunlight, on circling approaches etc., it can be difficult to see the screens without the shades in some attitudes/directions of sunlight.
There was a case of an early 320 (German?) that aborted and caused a serious head injury with the old map light - thus I understand the reason for the redesign?