It's a rule that doesn't really make a lot of sense to me. Most 2 year courses have 4 semesters - so they are bound to get 3 years PGWP for 4 semesters.
Something like George Brown, which has 3 semesters per year, which would mean a 1+1 there will be 6 semesters - so they get 2 years PGWP for...