In the ECAS explanation is mentioned, the following about DM.
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Medical Results Received by CIC
We have received your medical results. We will contact you only if additional tests are needed.
Approval Status Determined
Your application will be either approved or rejected. We will inform you of the decision in writing.
Permanent Residence Status Determined
If your application is approved, we will send you your permanent resident documentation and a letter saying what we need to finalize your permanent residence.
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So maybe the VO that processed you application is very workful and decided to updated the status right after receiving the Medicals.
Be positive and hopefully within the coming days, you will hear something
In my case, the situation was the opposite. I got the PPR while the status was still IN PROCESS. After 4-5 days, the status was set to "DM"