The commands in their example are not equivalent. The ps | grep thing searches the full command line including argument while ps -C (and, presumably, the psc thing) just returns the process name.

Should you for some reason want to do the former, this is easiest done using:

  pgrep -u root -f nginx

Their other slightly convoluted example is:

  psc 'socket.state == established && socket.dstPort == uint(443)'

  lsof -i :443 -s TCP:ESTABLISHED

It has process.cmdline as well as .name

Many new tools appear because people don't know how to use the existing tools or they think the existing tool is too complicated. In time the new tool becomes just as, or more, complicated than the old tool. Because there is a reason the old tool is complicated, which is that the problem requires complexity.