The offseason it what makes an 800m runner capable of, the track season is what makes them faster.
Yes, I recommend offseason work be done using continuous runs, but not all of the training has to be that way, I just ask that once a week a 8-12 mile run occurs. I believe the benefits derived from such training are unrealized by a majority of runners. I also believe it keeps runners fresher from track season because the work is more pleasureable than continuously gutting out 200-400 repeats or intervals. Another reason I ask my kids to put in miles during the offseason is not to gain unwanted weight from sitting on their butts.
As for your scientific assessment, 30 minutes of activity is not enough training to get the benefit of 45-90 minute session of running. That is the amount time required to stimulate muscle enzyme responses and build capillary bed within the muscle. The tempo runs you suggest are what pre-season and hard off-season days should contain. These tempo runs you suggest will not give you that unless do an Emil Zapotek or Vladimir Kuts workout.
I don’t consider myself a jedi-master of squat. I don’t consider the 1600/800 as compatible events at the HS level. A serious 1600m runner may make a good-decent 800m runner and vice-versa, you may not like how I train, and I may not like how you train. Many of my ideas are not revolutionary or even my own. Yes I use periodization or cycles any coach who doesn’t and feels that they should race their kids into shape is a fool. Sometimes I change my workouts mid-stream based on the performances I see in practice or races, if I see tired kids the I rest them, if I see fast kids, i give them more work. 2 weeks ago we cut everything, this week is our state track meet, we still trained abliet very lightly. We qualified 7 events for this meet. Looking at the State Meets already completed of schools of similiar size, my kids would have qualified in most of their running events and all 7 of these qualified would have placed at these meets. That won’t happen in my State meet because of only 2 classes and that my State is semi-large and deep in track and field. We had girls who never ran open 3200, 800, or 300H and all 3 qualified for state in those events, the latter 2 broke school records and all 3 are seniors.