I bet there is a clause in the owner's manual that says you can use lower octane fuel but you will notice reduced performance and mileage.
My S2000 uses premium fuel and it has the same statement in the owner's manual.
You might be able to get away with 89 octane, but I'm just guessing. At the end of the day hatchback owners should be prepared to use premium fuel if they are buying such a vehicle, otherwise you may want to look at a non-hatchback model, you won't really miss or feel 6 crank hp.
2016 Coupe Touring - Blue
2002 Honda S2000 - Silver with Blue and Black custom interior. Garage Queen.
2015 Jeep daily driver workhorse.