DMI changes every week, so calculation of DMI in this week shouldn't be slower, it is the same as in other weeks.
If reset of GS few days ago was only "grafic, not real", still "calculation" of GS in this week should be faster than in other weeks.
One more thing. I saw one untypical thing after this offseason update. As far as I remember in previous seasons DMI during offseason update never changed. During this offseason update DMI of few my players changed - it was cosmetic change, by 30-40, but I consider it as untypical.