Yes, when you run the command correctly from the cli it works. Did you just not read the entire post? The install script is not modifying the pbxstatus file correctly.
What you have in the installer is this and it does not match the word (case sensative) sendmail and the replacement is incorrect as well.
You still end up with this in pbxstatussed -i 's|SendMail| Postfix|' /usr/local/sbin/pbxstatus
I had to manually edit pbxstatus and change sendmail to postfix to get that screenshot to show it as UP.test=`ps aux | grep -c sendmail`
if [ "$test" -lt "2" ]; then
sendmail="$DN"
else
sendmail="$UP"
fi