Not entirely true however in the case described by OP I guess
@EE456 may be correct. People can do landing formalities in Quebec but in most cases people are transiting through Quebec so it is easy to prove that the person has no intent of settling in Quebec. I'm not sure how else one can prove that he/she doesn't intend to stay in Quebec.
To the OP check this link
https://www.canadavisa.com/landing-in-canada-as-a-permanent-resident-faq.html
Question 4.
Generally, the holder of a Canada Immigration Visa may enter Canada at any port of entry without difficulty. However, if you first enter Canada at a port of entry in the province of Quebec, you must have been accepted by Quebec and have a valid Quebec Certificate of Selection (CSQ) o
r be prepared to document your clear intention to reside in a province other than Quebec.