True. But there are differences when -v is used, as opposed to FS. Try this, where "nawk" is Lucent awk used by BSD

     cat > 1.awk << eof

     { print $ARGC }

     eof

     echo|nawk -f 1.awk FS=":"
     
     echo|gawk -f 1.awk FS=":"     
     
     echo|nawk -f 1.awk -v FS=":"

     echo|gawk -f 1.awk -v FS=":"