Following on from Rowan, the point of this method is when a face with diagonal swapped corners is easy to make.
Scramble: R2 F2 R U2 R U R' U R F' U
Face: U' F
CLL to solve this case would be L' U' L U' R' U' L' U R' U2 L. But then you're stuck with Yperm on bottom.
Instead, use the opposite CLL: R' U' R U' R' U2 R. Now, to finish, do R2 F2 R2. This can be cancelled in making the solve,
U' F
R' U' R U' R' U2 R' F2 R2.
This is EG-2, but most of the EG-2 algs at the time of the method's creation, weren't that great, so instead you used the opposite CLL, cancelled into R2 F2 R2 or F2 R2 F2.
Edit: I saw Rowan's post, but I swear all that stuff wasn't there

My post is a bit useless now, though I guess it has another example.