Transfer case shield

[gmyeah]

I was building a 2016 sierra 1/2 ton on the gmc site with a max tow package and I was allowed to choose the 'underbody shield pkg' as well. It is just a transfer case shield. I spoke to a dealer about ordering one and believe it or not there was no hesitation to setting up an order, but he mentioned the transfer case shield was not an option on a max tow package vehicle even though it allowed me online. Regardless if it is or not.....I assume the bolt holes exist to put a gm part on it. Why would this not be an option? Any thoughts? My trucks get used as a truck and this transfer case protection gives me some piece of mind. Should I bother investigating this.....or just go aftermarket.