Is that supposed to produce an immediate result?

One of the links on that page lead to an Apple page that suggested deleting com.apple.LaunchServices.plist from $home/Library/Preferences

Except that didn't provide an immediate result either. Likewise reboot didn't seem to make a difference.

Then I checked the Open With list again and the clutter was gone.

I'm happy it's fixed but puzzled about the delay, and uncertain which operation actually did the cleanup.