Mine does the same thing. I think if you scan just the PCM, then clear the codes, log out then check the history it does not show the codes.
To be sure you have a log, you must not clear the codes before logging out. I tried printing the DTC page after scanning for codes but the tool only prints a screen shot. So if you have many codes, you must print a page, scroll down, print another page, ect.
Be carefull if you want a record!
Kevin