Spotlight is incorrectly reporting disk read and write activity. It is reporting read and write as exactly the same figures, when they are not (using native AIX tools to confirm reads and writes are different).
Spotlight on UNIX for AIX 5.3 is using the column "r+w/s" from command "sar -d 5" to display data for disk reads and disk writes per time period.
iostat should be used as it separates out the KBReads/s and KBwrites/sec.
Waiting for fix in a future release of Spotlight on Unix.