I've read the study (or at least one of them) that discusses the effectiveness of these intervals on trained cyclists. They examined cyclists who hadn't performed any interval training for 3 months and had half the group doing high intensity intervals (6-8 5 min intervals at 80% of PPO with 1min rest). As you might expect, after 4 weeks their FTP and TT40k performance improved by 5-8%. This is likely similar to the type of improvement you could expect doing 2x20's every week but the 6x5x1's might be mentally easier to deal with.

I agree it's just another arrow in the quiver rather than a magic training regimen.