Yes, this happens in all previous versions
copy a file(s) from one folder [music] to usb [stuff]. copy another file from folder [pictures] to usb [stuff]. this will open two instances of file copy and detrimentally affect the performance of the device. 700mb [300mb]+[400mb] can take as long as 20 min to copy when 700mb normally copy's to the device in 1.5 min.
for explorer to queue the second(3rd, 4th) file copy operation untill the previous operation is complete.