There is a Bank of Motif XF Performances that are not installed as a Library. They are Factory Presets. So, no, there is no way to get rid of them, nor would you gain anything if you did.

There are 8 Library locations. To view the status of your currently installed Libraries:
Press [UTILITY]
Touch “Contents” > “Data Utility” > touch the folder labeled “Library”
The installed Libraries (those you loaded from a USB stick) will be listed, and in the upper right corner it will tell you how many of the 8 Library slots you’ve filled.

If you downloaded a File from the Yamaha site and installed the Motif XF Performances as a Library, (before a firmware update permanently installed the XF Performances Factory Presets, the Data was available as a downloadable File). Therefore, if you see the MOTIF XF data installed in your Library Folder, you can tap its box, then tap “DELETE”. The instrument will take a minute and remove the install. The Factory Preset Bank “Motif XF” will remain as Factory Presets.

Hope that covers all bases.