SERVER-61011 changed the serialization format for tokens generated out of RecordIds to use BinData instead of strings. We kept a backwards compatible path to deserialize the old format in order to support upgrades. Once we branch out 6.0 we can remove this code path: https://github.com/10gen/mongo/blob/39de467e0754eec484e75b792f3c3ba0381c4e47/src/mongo/db/record_id.h#L301-L304