What you're referring to is a marketing issue, not one based on the ability of the brush.

The Sonicare 3 Series comes with a "ProResults Gum Health" brush head.
The Sonicare 2 Series comes with a "ProResults Plaque Control" head.

If you want to make your own "Sonicare 3 Series Plaque Control" brush, just buy a "Plaque Control" brush head and snap it on your Series 3 brush.