My point, which I also made in another comment in this thread, is that law isn't code.
If you spend 3-6 months every year on a tourist visa in Canada working for your US employer, Canada's going to cotton on eventually and take action. If you do it a few weeks a year, you'll likely be fine.
Their test is "are you directly or indirectly competing with a Canadian worker?". If your employer is really ok with you being abroad 3-6 months/year then they should, presumably, also be ok with hiring Canadians or legal permanent residents to do the same work 12 months/year from Canada.