A key thing to note is that rent control in SF isn't quite what most people think of. The apartment itself is not locked to a specific price (which is how NYC rent control works, for example) but rather the lease between the landlord and master tenants can only increase so much per year.

For example you can have a rent controlled apartment renting for $500 a month, that tenant leaves, and the new tenants would sign for $3000 a month. There's no requirement the new master tenants would get the $500 a month. Whereas I believe in NYC's rent control the apartment itself is set at $500 a month, and anyone who moves in, that's what they pay.