The user data dir at the target system does not have any direct effect in OES, but it is available to all export templates generating PLC code through @configurationRoot.PlcHostUserDataDir.
Currently, the only object delivered by BCI using the path is the DataSetManagerAddon. The path is used as base path for the object parameter BinFileUserDataDirectory. The reason why it is configured on the target system is that non-windows target systems (like the Rexroth XM controller) need a different path.
In your usecase with the old DatAccess service, the bin file path is configured in the Data Management tab as in your screenshot. In this case, the user data dir on the target system is not used at all.
