VO2 Max workouts tend to confuse people fairly often because they aren’t all designed the same with the same expected outcomes.
VO2 Max is a physiological state, but it’s also the name of a power zone that’s roughly associated with most athletes’ VO2 Max. There are many different types of workouts where the power targets fall into the VO2 Max power zone, and many of them aren’t designed to have you working at your true VO2 Max.
A workout like Shir Kuh is a more “traditional” style VO2 Max workout that will likely have you working at your true VO2 Max During each interval.
Something like Shortoff +5 though is a completely different style workout that still fits into the VO2 Max training zone. The goals are very different as well. These shorter intervals are designed to get you to help you get more time in zone to improve neuromuscular fitness in addition to the aerobic benefits of simply pedaling hard. Think of these like strides for runners. The intervals are short and sweet, but the stress signaling is extremely effective while being less fatiguing than longer intervals.
Each type of workout has its own goals. If you’re looking to actually spend time at your true VO2 Max, a “traditional” long-suprathreshold workout will work well, but there are lots of other benefits to be had by simply working in this power zone for different durations. 
