I find it hard to believe that there are some stores stating they will have all sizes and models available. It is of my opinion that these sales representatives just want to drive traffic into their stores, assuming they can convince people to purchase what they have on-hand, as that is what most people do after they've invested the time waiting in line.
If you look around on multiple apple forums, feedback from all over the world is that silver, even more so gold, is heavily constrained with some Apple stores getting only 1-5 of the gold units overall.
I can tell you with a 100% certainty, that third party resellers such as Walmart, Target, Best Buy etc did not get any gold at all and limited on larger capacity 5C colors with Yellow being the most constrained.
Like anything, this may be subject to change as many stores receive their units via fedex/ups as opposed to their district distribution channels during the month of release to expedite their ability to meet demands,