Sideslip in a 747? I thought the main gear pivoted up to 14 degrees.
Crosswind landing technique is either:
(1) lower the upwind wing into the wind and apply opposite rudder to maintain track down the centreline. If the wind's strong enough, you'll land on one main first or
(2) apply a wind correction angle into the wind to maintain a wings level track and apply rudder in the round out to deposit you on the runway pointing in the right direction.
I was taught (2) first, but found (1) a better technique.
I have heard some discussion of (1) applying to low wing a/c and (2) applying to a high wing - which would make a measure of sense. Also a/c size might play a deciding role in the process: I have not had the opportunity to strap on something as large as in the photo.
Personally, I think the pilot accidently knocked the thrust control lever as he was reaching over to stow the approach plates
Good spot though