you have to press the button in real time then time stops and the game asks you wether ornot you want to use your reaction.
That way it doesnt slow the game down but still gives you time to think, in multiplayer there could be a time limit on it of course.
>TB and flow well, i dont think anyone said TB is fast, just that it isnt neccesarily slow. Hard fights are certainly not much of a difference. Reactions dont work well in either system
Online TCGs have the same problem with stuff like MTGs instant spells. Or the stack in general.
One cool thing of tabletop stuff is the "retroactive" element to it