Yup, that seems to be the case. I had people in front of me with my country's passport and their passports were scanned and they simply boarded. I assume that in their case it said "board" since they have an eTA.CDNPR2014 said:right, and if it says "do not board", more than likely they will ask to see other proof that you're allowed to travel to canada, right? so as the other poster is saying, that means they are essentially asking to see your pr card or something else.
In other words, the "board"/"do not board" message can have many reasons (immigration, no-fly list, ...). But not having an eTA seems to be one of the reasons that gives a "do not board" message.