Comment 1 for bug 1977710

From what I can see of this postinst this looks to be a bug from adduser in debian itself - and would appear to come from https://salsa.debian.org/debian/adduser/-/blob/master/debian/postinst#L33 - ie. if the default value is unchanged then an /etc/adduser.conf.dpkg-save is always generated when the value of DIR_MODE is appended to /etc/adduser.conf.

Can you confirm if this also occurs when debootstrapping a system from debian?