Great question! The key here is understanding how cohorts are computed in Mixpanel.
When you create a cohort defined as "users who visited a specific page in the last 3 months," Mixpanel computes that cohort dynamically at the time the query is run — meaning it evaluates who is currently in the cohort based on the last 3 months from right now. [How Cohorts Are Computed]
So when you use this cohort in a month-to-date report:
The cohort definition ("visited in the last 3 months") is evaluated as of the moment the query runs, not restricted to the month-to-date window of the report.
A user who visited the page anytime in the last 3 months (even if they haven't visited during the current month) would still be included in the cohort.
The month-to-date date range applies to the report's event data (e.g., what actions are counted in the report), not to who qualifies for the cohort.
In short: no, a user who hasn't visited in the current month would NOT be excluded from the cohort, as long as they visited within the last 3 months. They would be part of the cohort filter, but the report would only show their activity within the month-to-date window.
If you want the cohort to only include users who visited within the current month, you would need to redefine the cohort criteria accordingly (e.g., "visited in the last 30 days" or a fixed date range matching the current month).
