For previous FSD Beta additions, there hasn't actually been a requirement for 7 days but actually 100 miles. The timing happened to be longer for the initial US public beta rollout as 2021.32.22 (original "button" release) became available September 25th while FSD Beta 10.2 actually adding people happened October 11th -- delayed from the original 7 days:
When doing more regular FSD Beta additions, people have reported that they got added in even within a couple days of opting in and driving enough distance while maintaining a high enough score. So I would think something similar will be attempted in that Tesla intends to have a FSD Beta release/addition 7 days after the button became available in Canada, but that might get delayed, and in any case probably actually requires a distance -- not time -- with Safety Score.