This is regarding why this bug is not observed in Stretch and earlier. D and Z skipping behaviour was introduced by http://git.savannah.nongnu.org/cgit/sysvinit.git/commit/src/killall5.c?id=1b659c8ebebd86be51095ab905293889a306ff01
to resolve https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=719273 Changes went to 2.92 of sysvinit. Stretch has sysvinit 2.88dsf-59.9 (not introduced yet) Buster has sysvinit 2.93-8 (already introduced)
