DV Info Net - Archiving project glacial slow in 10.1.3

I am trying to archive a project by 'copy to new library'. The current library that the project is in is about 260 GB in total, and I realize that apple inexplicably ditched the 'copy only used media' feature. That sucks...
Regardless, I highlight the particular 8 minute project and try to copy it to a new library on a separate USB 3 hard drive, 'include optimized media' checked, and after 3 hours, I notice only 11% is completed.
How is this so slow? I could not cancel the process, only pause, so I forced quit.
I am now copying the whole library bundle via Finder, which will take less than 1 hour total, but will use all 260 GB of space.
Am I doing this wrong, or does the normally speedy FCPX ground to a halt for a simple project archive?
I have no clue why they would ditch such a useful option as 'copy only used media'....