XOFF doesn't discard input; if you pause for too long, things will backlog, which could be a problem if we are reading directly from some program (rather than, say, reading the output of something disposable and disconnected from the source, like tail -f).
When pw isn't updating the display, it's still streaming and discarding the data, which is a big semantic difference. It means that the source of the data will not block, for one thing. But if you need to see all the data or search through it, then pw is the wrong tool, at least by itself. You need to make other arrangements to capture the complete data.