more about stopping myself panic mashing buttons.
I think the reality is that there's very few attacks in the entire game that actually demand superhuman reflexes, but what causes most normal humans to face difficulties is precisely that button mashing. I don't think your reflexes have gotten measurably better compared to before, but rather that your brain has to spend less time analyzing and finding the correct response to what's happening on screen.
Also, I think most people get better at the game through unconsciously absorbing the timing of various threats, to the point that you unconsciously know that that sword is coming down 0.5 seconds after beeing lifted up and thus know when to press L1 to parry it rather than actually reacting to when you see the sword actually coming down. Which is why new enemies with differently timed attacks can often throw us for a loop, we never really developped better reflexes, we just learned to fight other enemies through rote memorisation.
TLDR: You got gud, but not because of reflexes.