The listCollections command returns a readOnly field per every collection.

This field is true on all the standard views and can be true/false on a standard collection depending on the queryableBackupMode and recoverFromOplogAsStandalone server parameters.

In contrast, in the case of a timeseries namespace, we are setting this value to false regardless of the value of these parameters, which is inconsistent with the readOnly value reported for a standard collection.