The person is not drinking but all of the old behaviors they had while drinking remain.
They are not "old" if they are still doing them. Lying, cheating, manipulating, stealing, blaming etc.
When a person goes into recovery these don't change on a dime but they do start to fade. They start living the program in the program and outside the program.
A dry drunk maybe be caring, friendly and hopeful in an AA meeting but once they leave they are flipping off the driver next to them, stealing TP from the store and blaming their wife/husband/children/God when they get home because they are an alcoholic and they have to go to meetings.
A person embracing true sobriety live in their recovery night and day, in the rooms and out, at work and at home, in the store or at the restaurant. They are not perfect, no one is. They are human but you will be able to see and feel a change.
The dry drunk does not change OTHER than to not drink. Many sober alcoholic will act that way in the beginning. It can takes weeks/months for the person to live sober long enough to begin to behave sober as well.