Yes, that is mostly true. But the time to work on preventing swarms is about 6 weeks ago, for you. And you can do a split when you find queen cells, although that doesn't always work either. I had a swarm leave a hive that I had split about 2 weeks later...even though they were down to half what the original hive was.
It is a tricky problem figureing out all what to do, especially for beginners. The best way to avoid a swarm is to make sure they are really weak coming out of the winter...and that sure isn't desirable either....
Rick