I totally disagree with this. I'm sorry if you actually had to do this but if you get pure levamisole I put in just the front part of a teaspoon for 55 gallons and they were gone in two days never to return. I tried all kinds of these other treatments. Even lost fish due to crazy treatments that didn't do jack.
I did a good vacuum then treated a week later as directed and I've never had an issue again. With any worm for that matter.
It sounds a bit overboard to me as well, though I can definitely understand the frustration of a relapse. They recommend that you do three treatments about a week apart if I'm not mistaken. And definitely siphon the gravel. After that, you should be ok. Whether or not all that extra work is worth not having a mini heart attack every time a fish looks at you the wrong way .. I don't know haha. It was a stressful couple of months for me.