In AutoGetCollectionForReadLockFree we can change the RecoveryUnit's read source if we are on a secondary, so we are storing the original read source presumably in order to restore it when the AutoGetCollectionForReadLockFree is destroyed, however it's not used again after initialization.

I think previous versions of the Lock free auto getters didn't restore it either, so this might be fine, it's just a bit deceiving.