First, let me take a step back. Airline policies don't matter, because they can't override the law. The law has been that you have to refund passengers, full stop. Unfortunately, the federal government failed to enforce that law.
In terms of policies, in some ways Air Canada was the worst offender, in that they made a false proposition that if you bought a so-called non-refundable ticket, then they can just pocket your money and give you no service in return. That's nonsense. That's absurd.
In November 2020, WestJet made some statements that they would gradually refund passengers whose flights were cancelled by WestJet. We are seeing some progress with that, although in many cases what passengers are doing and what helps them to get money back is doing a statutory chargeback under provincial statutes if they made a purchase with a credit card.
With respect to Sunwing, probably they are also among the worst offenders. They first promised passengers a refund, as they should have, and then said they were sorry, but they didn't have enough money. Air Transat is also in with that. They have also been refusing to provide refunds.