How to process a space delimited environment variable with xargs

Does

echo -e 1 2 3 4 | sed -e 's/\s\+/\n/g' | xargs --max-procs=3 --max-args=1 --replace=% echo % is the number being processed

accomplish the task? The output seems about right:

1 is the number being processed
2 is the number being processed
3 is the number being processed
4 is the number being processed

I also tried replacing echo with sleep to confirm it executes in parallel, and it does:

echo -e 1 2 3 4 5 6 7 8 9 9 9 9 9 9 9 9 9 9 9 9 | sed -e 's/\s\+/\n/g' | xargs --max-procs=20 --max-args=1 --replace=% sleep 1