Sharded collections support a different namespace limit than unsharded ones. The documentation on our MongoDB Website, MongoDB Limits and Thresholds, currently reports partial information about this which needs to be updated.

I suggest changing the documentation in order to report something as follows:

• For featureCompatibilityVersion set to "4.4" or greater, MongoDB raises the namespace limit to 255 bytes on views and unsharded collections, and to 235 bytes on sharded collections.
• For featureCompatibilityVersion set to "4.2" or earlier, the namespace limit remains 120 bytes views and unsharded collections and 100 bytes for sharded collections.

Please note that this information is actually reported in a couple of places, i.e. "Naming Restrictions" and "Namespaces".