Why does the input to xargs is 1 string but without is strings in separate line?

I am trying to pipe file to rm via xargs. I understand that what I am tryng to do could be done by git clean but I am practicing the cli.

I tried this:

for files in $(git status --porcelain| sed 's/^??//g'); do echo $files; done | xargs rm -rf

but it did not work. I figured it was because when running this:

for files in $(git status --porcelain| sed 's/^??//g'); do echo $files; done | xargs

The files seem to be in 1 string separated by a space.

But when I run for files in $(git status --porcelain| sed 's/^??//g'); do echo -n $files; done the files are displayed in the console in a separate line.

So (if I am right on this) what is the difference between:

for files in $(git status --porcelain| sed 's/^??//g'); do echo -n $files; done | xargs

and

for files in $(git status --porcelain| sed 's/^??//g'); do echo -n $files; done

and the files in the second case are displayed each in each own line and in the first case it is one string? And how would I fix this so that it works with rm -rf?