I'm guessing the plates help with wind resistance for EPA mileage purposes, keep salt spray off the engine, trans, and associated parts to help avoid corrosion of steel parts, keep slush and ice water off the turbos, etc.

Looks like a nice job on Ford's part. I'm sure those plates cost a few bucks, so they would not put them on if there was not a good reason.

Edit--I remember reading that the EB turbos and exhaust system run hot, looked it up, and noted that max operating temp of the turbos is 1740 degrees F. Yes that's 1740 degrees. Imagine hitting those turbos and exhaust manifolds with a giant splash from a puddle of salty slush that is below freezing temp. This makes me think of the term "thermal shock"... Plus I can imagine setting a field of tall grass on fire pretty easily.

George