Unfortunately that's pure poppycock. They claim they're dosing the bottles to 15 ppm of N2. That would me 15 milligrams per liter of dissolved N2.http://www.breweryhistory.com/journal/archive/162/Orval.pdf
This mentions Orval adding nitrogen at bottling. Interesting, I’d never heard of that.
A quick calculation shows that this correspond to N2 saturation at 25°C for a partial pressure o 0.26 bar.
OK, let's set aside the fact that you have around 8 grams of CO2 per liter and only 15 milligrams of N2 and that's 500 times less N2 than CO2 so how is that going to make a difference in a foam bubble that will be made of 99.5% CO2?
Let's just apply gas laws and determine the equilibrium pressure for 15 ppm of N2 at 25°C. I'll spare you the calcs and just give you the result: 0.26 bar absolute pressure. Wait a sec, air is 78% nitrogen, at a nominal atmospheric pressure you have almost 0.8 bar N2 partial pressure. This means that simply by exposing beer to air you would get three times the amount of dissolved N2 that they claim to be actively dosing in their bottles...
So basically they claim to be dosing N2 in the bottles by actually taking away? Does that make sense to you? To me it certainly doesn't.
I must say the amount of hype and misinformation circulating on the topic of nitro serving is really astounding.