Although negative reactions and grievances in all their forms are reduced substantially by taking the Steps, by no means are they eliminated 100%.
What happens is that they're removed: they're moved out of reach, so, whilst still present to some extent, they are no longer controlling us.
Being free of resentment therefore does not mean 'never reacting' but instead means not being imprisoned by negative reactions and grievances in all their forms. Though the substantial reduction in their severity, frequency, and duration is very welcome, and there may be many things that one ceases to react to negatively at all ... sometimes quickly, sometimes slowly.