This has absolutely nothing to do with preventing long distance or local charging. Especially since this price increase / structure will only apply to Model 3 owners.
It would also apply to any Model S or Model X purchased since early 2017 and later resold since Supercharging doesn't transfer to the new owner. It would also apply to any Model S or Model X purchased without a referral code as the referral code is the only way to get free Supercharging on those cars.