As I said before, there a different clauses which make sense in different situations. One can have another permit, one can have a maintained status too or there may be a temporary public policy that grants you an authorization to stay (this has happened during pandemic).
I am not sure if this is related to this discussion. There can be situations in which a person can or can not apply for a new status. That does not absolves IRCC of lying on its authorization letter (the permit; study or work).
Not so fast! There are legal doctrines regarding change of regulations or laws such as "grandfathering" -- (
https://www.investopedia.com/terms/g/grandfatherclause.asp#:~:text=A grandfather or legacy clause,often for a limited time.). This is to reach a fair compromise and avoid unfairness.
It is not possible to simply take away a privilege which was initially granted without providing a ramp off and it is often frowned upon or rejected in court of law.
Very likely, it will get challenged in court of law as an unfair policy. They can change policy that any study permit issued after XYZ date will NOT have a work authorization but revoking the existing privledge will lead to a legal quagmire.
Thing is, for any government, to be a government and have a rule of law, they need to have a rules which follow established legal doctrines and due process. This is what separates a court from a kangaroo court and governments from mafia.
If your country does bait and switch as a legal policy (like enticing students with work authorizations and suddenly revoking working privledges), it will be termed as a mafia and not a government. If it does it as a habit, sooner than later people will wise up. There are legal and fair ways to achieve the desired policy goals -- like reducing intake and reducing or eliminating work authorization for incoming students but tactics that are foul will end up hurting Canada and will set really really bad precedent.