The behavior is controlled by ~/.mini-dinstall.conf and described in the mini-dinstall.1 man-page.
# Whether or not to make .changes files unreadable to others by # default. This will protect you from other people unexpectedly # uploading your packages. Please think carefully about your security # before you change this! chown_changes_files = 1 Please, close this bug report. Best regards Heinrich Schuchardt