This is on account of the very different way in which the systems work. Priva Blue ID is based on the more modern Ethernet system and TC8 projects therefore save much more (meta)data on the controller than TC6 projects.
A controller only sends encodings to the cloud. To know what the encodings represent, the cloud needs the metadata for the project. The code is used as the basis for searching for the corresponding text in the metadata.
The Cloud Connector can retrieve the metadata directly from a TC8 controller, but not from a TC6 controller. For TC6 projects, this data needs to be retrieved from the project database using the 'TC6 Metadata uploader'. This can be downloaded from My Priva (https://my.priva.com) if it has been enabled for you by the administrator.