No pass & reservations are two different things.
In case of  reervation compulsory trains you have to show both reservation and the pass
On reservation optional trains the conductor usually wont ask for reservation (Only in case 2travelers wants the same seat. ) as then the travler with reservation get´s the seat as he paid for it.

NOTE; for THIS train and as it goes into IT you need a special 10€ extra supplmt-as too many passholders use it (applies also to all other trains from DE/AT into IT)-this is as such NOT a REServ. Conductor will want to see this extra-and is likely not at all interested in the seat-res if you also have that.  Maybe you confuse the 2. But in EUR its the age old custom that normal traintix are anonymous-trains are not planes.

Hi, I think this is the first time I hear about this, but in principle I am only obliged to have a reservation, right?

Hi, I think this is the first time I hear about this, but in principle I am only obliged to have a reservation, right?

Usually yes but on this train they made it quite unusual as you dont need a reservation but you have to pay a supplement.

 

Here a short manual how to pay the surcharge
 

Hi, I think this is the first time I hear about this, but in principle I am only obliged to have a reservation, right?

Thanks for the info. However, as according to your article it is possible to pay on the train, we'll wait until they ask us to see if we can get rid of it :)

Hi, I think this is the first time I hear about this, but in principle I am only obliged to have a reservation, right?

Yeah the article is quite old on the offical information page is a warning that you have to pay in advance. Otherwise you risk to pay a onboard surcharge aswell.