12V in, 1V @ 12 Amp Out, Buck, Why 100 Amp MOSFETS and 60A Inductor?
Webench is a nice tool, but sometimes it makes strange suggestions.  You have to use some common sense.  I can't say for sure why it picked this configuration, but I have a couple of potential ideas.  First, each given controller/topology seems to only have a few options for secondary parts like MOSFETs.  The tool simply may not have many options to use with the LM3150, and this is the only one that meets the requirements.  

Second, you have selected "optimize for efficiency".  It is possible that it picked these high current MOSFETs to get a low Rds(on) for highest efficiency, even if it is a bit silly.