They just ignore the regular community accepted meaning of words... so, 'not required' is true in the sense that noone puts the proverbial gun to a person's head saying 'I require you to accompany me in the D2D work...'
...but they do say things liker 'if you don't go on the D2D work, you are putting a figurative gun to your own head by displeasing God and denying the obligation Jesus put on you to for forth and preach'...
I think the community would take that as 'required', but the JW can say it with a straight face and almost believe it themselves... all they do is redefine words to suit their version of truth.
GIVE ME FREEDOM FROM RELIGION