The Sunnah method is to perform Sujud al-Sahw after Salaam.
On the more correct view stated here, one Salaam to the right is sufficient before the two Sahw prostrations. Some jurists preferred giving both Salaams before them.
If the two Sahw prostrations are performed before Salaam:
• the prayer remains valid;
• the act is disliked in the light sense;
• the Sahw prostrations are not repeated merely because they were performed early.
So the course no longer says 'only one Salaam is legally possible'; it presents one Salaam as sufficient on the more correct view.