On the subject of life bars, which we danced around a little, and Igarashi's quote, I don't see why a perfect run necessarily needs to be defined as no miss. This doesn't deviate from the spirit of what Iga said, that the developer should have a perfect run in mind, but that a perfect run shouldn't have such a crystallized cross-implementation definition as "not getting hit". I think that's a bit lazy, a bit constrictive. As we said of SNK, games with life bars build in the idea of exchanging damage and gambling life. You don't always choose a strategy that preserves life so much as you choose the one that gets you through the level. If you have half a health bar, it may actually be safer to go in and swap some light but guaranteed punches than try to wait out a pattern, risk missing a small opening, and take two heavy hits in return. Played Ninja Gaiden or Mega Man recently? Then I'm sure you were in a situation where you just decided to take some hits while mashing the attack button. Sometimes that is the best way to play.
Think from a speed-runner's perspective. Someone who has minimized the time it takes to get through every boss fight. Would you say that they have any lesser grasp on the strategy because they might take damage in some way that speeds up the fight? The end goal is only to win the game. So why couldn't a developer define a perfect run that way? Why can't a perfect boss run be built around something more than dodge, attack, dodge, attack?
I think there are all kinds of perfect runs (in SNK and other games) and they might not have an exceptionally clean or singular-per-game definition. When the goal of the game is simply "defeat the enemy and survive", a player can find their own definition. It may be to beat it as fast as possible or without getting hit, or to beat it while showing off every technique or without blocking. Maybe it's as grey as beating it while retaining 75% of the life bar. I'm not saying anything can be anything as long as you can win - that's the exact opposite of Igarashi's point - but that what the developer should be focusing on is that there is something that the player can maximize so as to improve their play. It's kind of like what I said in the podcast about the player not necessarily needing to master the game to get the most out of it, but needing to be able to see the path to mastery. You get better at something to the point where it stops being fun, and that's the perfect run. If the developer has an idea of that perfect run, a way to get the absolute most out of the fight, and has put in ways to strive toward it, that's good enough. That to me is the generalized aspect of Igarashi's quote when removed from the setting of no-miss runs.
Scoring / rating / achievements are obviously the simplest way to get players engaged with this mentality - unsurprisingly, a couple people mentioned in the podcast that they've only taken on challenges when offered these carrots. We scoff at these tools sometimes, but if they help people to get more out of the game, they have their use. If the developer has a particularly obscure notion of what makes an interesting "perfect run", that's something they can nudge the player toward with a trophy or a bonus challenge.