You can check flatfile.html for all of the reported results fields. But you are correct that I/O rate and MB/s are not reported separately for reads and writes.
You should be able to calculate those values based on the achieved read percentage. This would be fairly straightforward when reads and writes are using the same I/O size, but you will need to take the I/O size into configuration if it is different for reads vs. writes.
Hope this helps.