It is not a 3rd party website *facepalm*. Go to
www.bilstein.com (the official Germain website btw). Go to the upper right corner of the site and click e-catalog. That will bring you to the link I posted. It doesn't get more official than that.
The copy pasta is between the same series of dampers, they use the same description for ever B6 damper. Go to the US catalog, and click between different car's B6 dampers.
These dampers were posted to the European catalog first. It did say twin-tube at that time.
Believe what you want, all the proof is given. Don't forget, you can always call the Bilstein US' phone number. They'll tell you they're twin-tubes. Hell, they've been known to tell you the numbers for the compression and rebound measured typically at the "knee". But what do I know, I've only checked the *official* Bilstein catalogue weekly, posted the good news about them the moment I found out they were listed, cheered when the US site finally has the listing posted, and finally ordered a set last month when the Canadian distributor had a sale on them.