Air carrier landing runway 28L at sfo was confused when told; 'following a B757 5 miles ahead'; when...

Narrative:

Ten mile final; still talking to norcal approach. We are maintaining visual with traffic off our immediate right that is landing 28R and we have been cleared for the visual 28L. Norcal tells us 'your following a 757 5 miles ahead switch to tower now 120.5'. Ok; now I'm confused. I see a B737 5 miles ahead landing 28L and a B757; just off his wingtip that is landing 28R. So I ask the norcal controller to repeat and he says the same thing; 'following a 757 5 miles ahead' we switch to tower and land on 28L as cleared. My question and confusion is why do they say I'm following an aircraft that is not landing the same runway that I've been cleared a visual approach too? As tightly spaced as the runway configurations are in sfo it would seem it would be a lot clearer if they told you to follow the aircraft that is landing the same runway you've been cleared too.

Original NASA ASRS Text

Title: Air carrier landing Runway 28L at SFO was confused when told; 'Following a B757 5 miles ahead'; when the B757 was inbound to Runway 28R and a B737 was immediately ahead for Runway 28L.

Narrative: Ten mile final; still talking to NORCAL approach. We are maintaining visual with traffic off our immediate right that is landing 28R and we have been cleared for the visual 28L. NORCAL tells us 'your following a 757 5 miles ahead switch to tower now 120.5'. Ok; now I'm confused. I see a B737 5 miles ahead landing 28L and a B757; just off his wingtip that is landing 28R. So I ask the NORCAL Controller to repeat and he says the same thing; 'following a 757 5 miles ahead' We switch to Tower and land on 28L as cleared. My question and confusion is why do they say I'm following an aircraft that is NOT landing the same runway that I've been cleared a visual approach too? As tightly spaced as the runway configurations are in SFO it would seem it would be a lot clearer if they told you to follow the aircraft that is landing the SAME runway you've been cleared too.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	860613
Time
Date	200911
Local Time Of Day	0601-1200
Place
Locale Reference	SFO.Airport
State Reference	CA
Aircraft 1
Make Model Name	A319
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Air carrier landing runway 28L at sfo was confused when told; 'following a B757 5 miles ahead'; when the B757 was inbound to runway 28R and a B737 was immediately ahead for runway 28L.