It is and it is not.
When a person arrives at POE he is asked by a border officer what is a purpose of his visit? And depending on answer and Border officer's judgement a person could get just an entry stamp (and that means he can stay in Canada LEGALLY for 6 months) or to get a stamp AND a hand written date of requested exit under the stamp. And that date could be any date for a period of time shorter than 6 months.
If a person did not get "an exit date" and stayed for 6 months and leaves in time then CBSA supposes he will stay in his country for a long time living his life in his home country: working, studying, dating, visiting relatives, traveling to OTHER countries. If rather then that , after couple of months in his home country he appears at POE again asking for another 6 months stay in Canada then there definitely will be questions WHY such long visits , so often and for such a long time?