Boney talks about them separately and, importantly, talks about them differently with regard to the benefit the training sword provides, which strongly implies that they are distinct options. So there are really two stretch goals for Branarhune, not just one, and we need to decide if we want to do both of them or just one of them.
If given the choice, I think I would prefer to just refine the guard bypass for Branarhune, rather than do the double-tap, and then call the style done, since if the guard bypass works it does the thing the double-tap does but faster, and Boney has said that the training sword would be a "big help" for the guard bypass, meaning we're in better shape to do it than we were before.
The thing I'm worried about is us not being done with the style at the time we thought we would be done with the style, or finishing the style in a suboptimal way because we misunderstood what our options were. As I outline above in this post, I think there's good reason to believe that there are six potential actions for Branarhune, not five: four base and two extra.
Boney, if you see this, can you shed some light on what the potential "stretch goals" for Branarhune are? Is it just the double-tap as a workaround to failing the guard bypass like we'd been thinking, or are both the double-tap and the guard bypass available?