Allen-Bradley controllers have always considered the data tables to be part of the user program and there is no "partial download" feature. That's just the way they work.
One workaround is the Tag Upload/Download Tool that uses RSLinx as an OPC server to bulk upload data table values to a PC and then bulk download them to the controller. This can serve as a "preservation" method for data that has been developed over time in the control system.
This tool is included with RSLogix 5000 (installed into the RSLogix 5000 Tools folder) but can also be obtained from RA separately.
It allows you to upload data tables and save them to a text file, which can then be downloaded back to the controller separate from the program. It's very handy if you have a program you modified offline that you want to download, but want to preserve the current data in the PLC.