From what I read on your link to the combine forum was they were pulled into a scale in CALIFORNIA and the TRUCK and TRAILER they were hauling a combine on had a brake inspection and 1 brake was out of adjustment.
The rules are the same for the trucking industry on both sides of the border.
Yes the rules for Motorhomes are different in Canada and you are required to have an air endorsement on your drivers licence and your licence will be appropriate for the weight of your RV. You don't require a full CDL.
My wife inquired about getting certified and it was a 7 hr course at a commercial driving school for $200. The term 6 pack adjustment may be confusing but if you google air brake adjustment I am sure you will get an answer.
If you don't think a DP operator should know the basics of what they are driving then why do commercial drivers need that?
I have read many posts on here of people asking questions that have absolutely no knowledge of what they are driving and some of the answers they get are even more frightening.