The problem with your logicrunning a good solid 800m will improve a runners potential stride length and bio mechanics over all distances if they properly train and increase mileage over time is that it's a different energy system altogether. It's running power for two laps.
But as you increase the race distance, that system becomes useless unless you are capable of running relaxed for 9200m and have energy to change systems on the last two laps.
Since you are talking 17min 5k, it makes more sense to train for a 5k-10k (similar systems) to improve your times.
Ill give you myself as an example.
I never ran raced a 800m, fastest rep is a 2:17. It would take everything to break 2:10 and impossible to break 2mins with any of my training the past 10years. I run on avg 40-50miles a week, and that's being generous, it's probably closer to 40miles/week. Ran a little track but most of that 10years is on the road.
A friend of mine as a PB of 1:49. As multiple 1:51-1:54s and at anytime we have raced together is capable of running sub 2min on any day of the week. He's been off the track for the past 4 years running road and doing more mileage than me. 60-70miles a week on avg.
My PBs from 5k and up are all better than him.
The last 2 years we have raced at least 10 times on road, I only lost one race because I had to walk part of it, had a bad leg cramp.
We are at the same level (we can push each other in training). We run in the same pack in races, but my efficiency on the road is better than his. No matter what he tries tactically, I beat him everytime because he will get tired quicker than I will. That's because like I said earlier, we are running a different system, now if I ran 4:00/km for the first 4200m and he was in the race, then I would agree with you that his 800m stride would be useful.