Could it be that people getting the comped status are those who earn relatively more MQSs than MQMs and DL is implicitly looking at what the status would be if some or all of the MQSs rolled over?

Even if someone hasn't been flying much during the last couple years, it's not that hard to have enough MQMs for status due to rollover if the person takes relatively long flights, but people who fly a lot of short connecting segments don't get much rollover.