Prior to this provision, people on
full pensions who were exempt from SS contributions (such as teachers in many places) were able to still collect those
amounts (which were never earned through contributions) even though they had quite significant pensions; that led to
subsidies being given to people that didn't have as much need for them, as opposed to the indigent people who did need them.
Alternatively, you can choose to pay the
full amount of the premium yourself each month and claim your total premium
subsidy on your tax return the following spring (this is not a common option, but it's available and the choice is yours).