I have not played Sekiro, but I have played an indie knockoff called Kanagi Usagi, so I’m basing my understanding on that.

From how it felt, the health bars are a decoration and the real boss health is poise. I get what they were going for, but it causes a lot of stress for any interruption like healing or long enemy attacks that cause their poise to regenerate, feeling like your effort and time was wasted.

A game I liked better in every respect was Another Crab’s Treasure. You build poise even just by hold-blocking, but your “shield” is a limited resource; one you can choose to invest in with RES. It keeps the idea of encouraging you to keep pressure, by building poise damage on regular attacks, but also punishes you for dodge-rolling as a default for every attack (you’ll never get a “capsize”).

And yeah, ACT is a bit easier; but I’d say its chosen level of difficulty made it a more enjoyable game.