Kazam,
every time I have run the script, it has been like this or worse for the DAC.
I have no definitive insight, but my theory is that the DAC is just outputting uncalibrated values (vs. values calibrated with the current calibration), which makes sense.
Having run the script many times during development, I have anecdotal evidence that this is what happened. I have more than once written totally erroneous calibration data and the supply was then totally unusable, but, even after that, the calibration script turned up similar results. So I assume it is indeed just ignoring current calibration values altogether while running the script. And in my experience, the DAC is off by similar (noticeable) amounts during calibration, with the ADC being very close.
Laurent