> you received a significant discount for committing to a year, so you still owe them for the remaining months if you cancel early. I didn't even realize I had signed up for a one-year commitment

Does this law apply retroactively?

You wouldn't have a claim under the "straightforward cancellation process" part–same way this law doesn't enable one to walk away from a long-term lease for shits and giggles. But you may under the "clearly explain subscription terms to you" bit.