It is nowhere written that "may be" means that education does not matter and "usually" means that education is strictly required.Your reference is partially correct and also 100% applicable for the original poster here. However just for our future reference, few NOC (specially management, doctors, architects, dentists lawyers etc.) does need to meet education requirements. Where NOC description says education requirement "is/are required" without the term "usually" or "may be" means that education requirement is compulsory to claim experience points for that particular NOC.
Hope it helps!
As far as docs and lawyers are concerned we all know that one cant claim himself to be a lawyer or a doctor anywhere in the world without their relevant degrees. But most other job titles are different in some countries you require relevant education for this in other you can perform that job without relevant education in that field.
For example my friend was a teacher and he was MA in economics in my country he did not required B.ED to teach but in canada you must have B.ED degree to teach and you can search Noc 4032 it also mentions one should have B.ED to teach but he got the PR and now doing economic related job in canada.