Jim,
Heavy wake turbelance is not wavierable. Tthe 7110.653-9-6 f says: Separate IFR/VFR aircraft taking off behind a heavy jet/B757 departure by 2 minutes. Paragraph h states: Air Traffic controllers SHALL NOT approve request to deviate from the required wake turbelence if the preceding aircraft is a heavy jet/B757.
Now for the 25L and 25R issue. Since FAM's have ceased to exist I see more and more situations like this occuring as well as controllers changing arrival runways with short notice, because they don't know what you the pilot have to do in order to run the numbers for the new runway.
You called in advanced requesting 25L, when you called for taxi and the controller gave you 25R, all you should have to say is, "we coordinated earlier with Ground that we require 25L". Odds are the controller forgot, or forgot to brief the relieving controller. When I have a pilot request for a specific runway, that I as ground approve or said to expect, I write that runway on the flight progress strip so that I don't forget. If the requested runway goes against the grain then I will warn the pilot to expect a delay and if possible how long will it be.
Jim, If you jump over to the NATCAnet Public BBS
http://www.natca.net , Click on the About NATCA link, then click on the Public BBS you can post specific questions and comments like this that odds are will be answered by the controllers that work at that airport (or I will forward your message to the NATCA Facility Rep for a response).
Sometimes a specific parellel is assigned based upon what direction your turn after departure will be so that we can reduce or eliminate the possiblility of you crossing the departure corridor for the other runway, that may have been the case here, but I'm not familiar with SFO so I don't know.
Mike
NATCA FWA