It seems that most of the other utilties use DMA to access the flash memory. I’m not sure whether openOCD uses the DMA mode for EJTAG in this case. I found that there was a patch submitted some time ago to support this. At first sight, I can’t seem to retrieve any of the debug messages involved in openocd’s output for this.
The switch should be made according to the IMPCODE of the board, so this should be transparant for most cases. Will need to do some more investigation on this.