VBF only has photon in intermediate state

Hello,
I was trying to generate VBF with anomalous couplings, and though the rate should be dominated by WW fusion, I only find photons in the LHE file. Is this some kind of calculational technique? I checked and none of the bosons have very high p^2, so it's not clear to me why the W/Z boson masses can be neglected.

I also want to plug the momenta into the matrix element to do some checks, so should I use the matrix element with photons or W's? And there's no AAH vertex that should contribute to the process, so it's a bit confusing.

thanks
Ralph