But it seems the necessity to punch an additional Roman has always been just a myth, huh?
The combo state (after "COMBO" effect) lasts 30s. When it starts, its time left is being eaten away. Call this combo time left.
This combo bar has a fill value, starting 2.96 indicating how much of it is filled. This fill value is also being eaten, 0.0987 at a time, so the total time in seconds is 29.989.
When the game runs, the combo time left is subtracted from first. Normally, this would mean it ends first, even though it takes longer (this depends on delta time though, but normally it's 0.015, so 30-0.015=29.985, ends earlier). No flybash, because this sequence resets the proper punching state.
If you punch a roman, the additional time is added to combo time left, and it forces the game to update the combo bar fill value. However, before it does, it eats away at the combo time left. So the combo fill value effectively loses some time, hence it shall finish first.
If it ends first, it skips the part where the punching state is reset, because it hasn't a flag hasn't been reset yet (combo time left hasn't finished its 30s timer!).
Interesting! I'm not sure I've grasped it entirely yet, but thanks for the research!
I wonder how does the merchant tie into this? Is combo fill paused while we're at the merchant, while combo time left keeps running down, finishing first if we don't punch a Roman after merchant?
Seems like the combo fill value is NOT updated, but the combo time left is. So it gets ahead, ending first => no flybash. But if you hit the roman, it grabs the on going time left. You can SEE this, because the actual combo bar DECREASES visually!
yeah cool, that explains it!
I must say, it's very satisfying to finally understand glitches years after they were found x)
Coded with legs.

I wanna see how tardises are possible, but it's such a mess XD
not having to do the punch-not-kill thing anymore will save me some seconds for sure x)
We gotta test that shit, cuz there could be some code that does stuff... you never know... just in case :D
I'm also going to do some any% runs soonish :)
Careful though, you NEED to hit them AFTER the combo effect.
because the fill is not getting updated during the combo effect?
what else can pause the fill, but not combo time? Druids presumably... and what about the pause screen?
Pause screen pauses everything.