Tabata intervals are not useful for non-drafting triathletes of any distance. I actually can't think of a workout that has a worse cost/benefit ratio. Lets start with physiology.
We have two energy systems
the aerobic system is more efficient. As endurance athletes, we want to train the aerobic metabolic system to produce most of our ATP throughout our event, because it is more efficient and will get us across the finish line faster.
the anaerobic system is less efficient. athletes who perform shorter events rely on this system to help produce power/speeds beyond what the aerobic system is capable of. The problem with this is that you will fatigue much more quickly once activating the anaerobic system due to its inefficiency.
Improving our aerobic system can be done by pushing up the aerobic ceiling (vo2max intervals) or by improving aerobic efficiency (endurance and threshold training)
When you do short explosive intervals you are activating the anaerobic system, prematurely fatiguing your body and thus not taxing the aerobic system for nearly as long longer sustained interval.
vo2max intervals should be done at your 8-10 minute power/pace
ideal lengths are 2-5 minutes, with equal rests.
I usually cut down the quoted parts of posts to only the relevant bits but almost every sentence of your post is misguided so I quoted the whole thing.
Tabata training has been shown to increase VO2Max.