I too noticed this. For me it was negative. It's now way too loud (-48 dB) with Dirac on, and it sounds like the room correction isn't working properly. There used to be little to no difference on the sound level with Dirac on vs. off.
I have filters made back in July 2020 with Dirac Live v2.5.3. I tried exporting them again with the new Dirac Live v3.9.7 but it didn't help. Interestingly, the v3.9.7 changelog says: "Fixed the known problem where some NAD devices got substantially louder sound with Dirac ON than with Dirac OFF." Already sent an email to Dirac on how to get the filters working correctly again. I would prefer to not have to re-measure the system.