CollectionCriticalSection is only used by MigrationSourceManager, which already validates collection metadata at construction and again before enterCommitPhase() via _getCurrentMetadataAndCheckForConflictingErrors().

The tasserts on getCurrentMetadataIfKnown() at catch-up and commit entry duplicate that work on the happy path and only guarded a narrow race where another thread could call clearFilteringMetadata_nonAuthoritative between MSM’s check and acquiring the CSR lock.