After SERVER-79177 we added the concept of an unsplittable collection, which contains an entry on config.collections and a single chunk. Currently, this is not supported by most of the code, causing that for example if a command ends up using UNSHARDED as placement version, the shard will always throw SSV for unsplittable collections.

We should momentarily, while all code in server is not compatible with unsplittable collections, under a feature flag, disable throwing in shards for unsplittable collections.