You'd likely get a failure to reform, based on the fact you'd be intentionally making it harder for the opposing skater/s to legally re-enter and form a pack, which is the opposite of what you're meant to do.
Something similar which does catch people out: when knocked out of bounds, sometimes it's better to just stand there and wait for the skater to move forwards (so you don't end up a goat, for example). If you're stood at a side of the track, then there's a "no pack", and you don't immediately move to re-enter, you get a failure to reform.
Bonus; the person stood off track likely is looking smug because they know if you're blocked off the track you don't need to re-enter. When smug people get penalties is the best.