Great topic @peter17
The idea of focus is to help us understand what the training effect of a ride was. If you ride for 2 hours and then add some sprints in, what is the overall training stimulus of the ride? It can’t be pure endurance - you put strain on your peak energy system. Alternatively, it can’t only be sprinting, as that would exclude the endurance work that preceded the sprints. Therefore, the overall stimulus must be somewhere between, right? Focus tell us this.
However, Focus is only half of the equation - this is where specificity comes into play. The ride you mentioned above may have had a 6 min focus, but the specificity was so low, that the ride could still be considered mostly an endurance ride.
It’s a bit of an abstract concept/chart, but hopefully you can follow along. If we plot focus & specificity on a polar chart, where focus is the angle & specificity is the radius, we end up with something similar to this chart I’ve graphed below (NOTE: this is not exact/to scale, but simply for illustrative purposes).
Anything in the blackish/grey area could generally be considered an endurance ride, since the vast majority of XSS of that activity will be LOW XSS. However, as you add more HIGH XSS throughout your ride, the specificity gradually increases (moving you closer towards the outer edge of the chart). This results in a ‘mixed’ specificity. Continuing to add even more High XSS will push the specificity even higher (towards the edge of the chart) into the PURE specificity rating, meaning that ride/activity was very SPECIFIC towards the focus duration you were training.
As an example, I’ve plotted where your example might fall on this chart (big yellow dot). Note that the angle/positioning of the dot still aligns with 6:00 Focus Duration, but the specificity would be so low that the ride could still be generally considered an ‘endurance’ activity (not a HIIT workout that develops 6:00 power). I created the chart mostly to help illustrate the example and further the discussion. Hope it makes a bit of sense!