Again, the math does not add up. There are inconsistencies that do not align. You're noting one element that can align when one set of the facts are considered, but it does not align with significant elements of the information provided.
While dealing 40 damage per turn could result in a resetting via healing that gave the later PCs a chance to contribute on the main foe - the entire premise for why the system was created points to that not being the expectation.
The PCs were dealing 550+ damage in less than 2 rounds - which means that they were averaging about 75 to 100 damage per character turn in every mock ups ... but yet the real PCs were also just dealing 40 per turn per notes.
Further - if you're run high level games, 40 damage a round is kind of odd for many PCs. How much damage does a high level fighter deal in round one? 2014, close to 200. 2024, closer to 130. How much does a Shapechanged PC deal at 17th level?
The underlying problem that required this system to address was that they dealt far too much damage for the normal rules to provide a good experience, yet in practice they dealt half or less of that damage.