One thing that I can tell you is that the job title is not of importance for immigration. Whether you are called a professor, instructor, researcher, etc. it does not really matter. Only duties, place of work (type of institution) and educational requirements matter. Someone can be called a "hygienic engineer" but if job duties reveal they are a janitor, this would be their NOC. (I am exaggerating, but that's how it goes).
The main issue is that Canada NOCs do not understand a difference between a tenure & tenure track job and non-tenure track. This is why many people who work in 4011 miss the research component (because they only teach), or miss teaching component (if they only do research). So many people work at Universities with a PhD but only do teaching (my wife's case) - is that 4011 because of education and type of institution, or 4021 because there is no research and supervising component? Similarly, if someone has a PhD and does teaching, research and supervising, but the institution is a college and not university, are they 4011 or 4021?
Essentially, they seem to think that 4011 = University + PhD + teaching and research; 4021 = College + MA (or BA, certificate) + teaching only. They didn't get the memo that various combinations are possible, and there is no indication what takes precedence (education level over type of institution?)
As far as I can tell, you fulfill more duties and education requirement for 4011 (the "may" duties can be ignored more or less, so don't worry about them). Like I said, my wife does only teaching (is paid for that; research is at her own discretion, which means they do not pay her for that. Is that your case, too?) She works at a University in Canada and her job is officially 4011. (As stated by the University - not sure if this is given by Canada officials or how it's determined).
I would say that the only thing you don't fulfil is "university" in the name of your institution. Does your institution have grad programs? Does it perform research? (Even if you personally are not paid for research)? This is a 4021 institution description: This unit group includes instructors who teach applied arts, academic, technical and vocational subjects to students at community colleges, CEGEPs, agricultural colleges, technical and vocational institutes, language schools and other college level schools.
On the other hand, since you seem to only perform teaching at a college, one can also argue that it's 4021 regardless of your education. So if you feel your institution is more along the lines of a college, then you can argue you are 4021 even with a PhD. (Though I do think PhD jobs are 4011, but don't take my word on it).