"Is it true?" Well it's your workflow, so you'd have to tell us whether what you described accurately represents what you're doing or not.

Presumably you meant, "is this a good way to do it?" My only critique is that you might want to use M-values, since they won't have the ceiling/floor effects. You might also want to stratify things by high/low/medium promoter CpG density. I've also seen people divide things into <20% CpG, 20 to <40% CpG and so on groups. Maybe that's worthwhile, maybe not (there's no best practice here yet), but it's something to keep in mind.