I love intervals! This sounds more like intervals to me than HIIT, but it's an awful darn hard interval!
From everything I've read, true HIIT is something you can't sustain more than 20-30 seconds.
All Out! But like you said, it's a modified version. I only bring this up because the biggest benefit you get from HIIT is the 24-48 hour after burn where your furnace is burning higher than it normally would. It's what makes it great for burning fat.
But other than that, I think it's great. I suggest doing some research on it if it's something you really want to pursue.