As noted, yes they are. Please go to http://www.sfgov.org and go to Mayor's Office of Housing and you will be able to see all of the details for Below Market Rate purchasing.
The program also doesn't address people that become disabled, have an asset such as a home or condo they can no longer afford and now are on disability. They don't qualify because they have the asset, even though they qualify on the income level. It seems as if the API segments addressed are addressed for political reasons and not to make home ownership more afforadable.
The BMR program is of course well intentioned but the housing needs of many are not being met.
Please see: http://www.sfraaffordablehousing.org for more details.