Totally agree. They are doing some sort of weird buffering.This really should not be an issue if the software is written properly though as I can plug the same USB drive into the cheapest Android tablet and it will instantly resume music from my 240GB drive.
I noticed the other day when I made a small change to one songs tags. I then put the drive back in and the car rescanned it. In the past the car would never rescan a USB drive if the root folder name was not changed. Obviously they decided against that somewhere down the line and now they seem to rescan constantly.
Maybe they got too many complaints from people who were upset that music they added did not appear.