In SERVER-77506  we introduced CollectionMetadata::getShardMaxValidAfter() that should return the timestamp of the latest data placement change for this shard.

Currently, this timestamp is calculated as the maximum validAfter of all chunks currently owned by the given shard. This value does not represent the latest data placement change for the shard because it does not account for the last chunk donated by the shard.

In fact the timestamp of the latest donated chunk is registered on the chunk itself that after the migration commit is not part anymore of the set of owned chunk by the donor shard.