No, those users always wrote more than 14 posts per period, so their counters, like mine, always changed strictly by 14. Although I saw those users whose activity counter changed with each post written, because they wrote very little in 14 -day period, but it's not about them at all.
My question is when is the Legendary rank given? Strictly on the days of recalculation of activity or on any day between periods of recalculation of activity?
If their posts and activities are always capped at 14 for each 14 days, when their lucky numbers knock their doors, they will rank up at the activity-recounting day.
Note that on that day and in that new 14-days period, they will rank up after they make at least one post and that post is counted into 1 new activity. Activity will be counted every one hour, perhaps.