Apparently you have a first generation Airport Express and those predate 802.11n and the 5GHz band.
Nope; I couldn't be engaged in this experiment if I didn't have at least a 1st generation "n" AirPort Express. (The older ones haven't been supported, i.e. configurable with AirPort Utility, since a few versions of OS X back.)
Here's what I"m seeing:
this screenshot shows that my AE isn't seeing any of the 5 GHz FiOS networks, while
this one shows that it
is seeing other 5 GHz networks at the same time.
Why do you have to create a network on your AE for Air Play? According to
this Apple article you just have to be on the same local area network.
Your linked doc deals with iOS devices, not Macs.
What you can AirPlay
You can AirPlay music from an iOS device to an Apple TV, AirPort Express, or AirPlay enabled speakers.
I suspect that playing music to an AirPort Express is an exercise similar to the one in which I"m engaged.
To run AirPlay on a Mac, your stereo must be plugged into your AE and
you must be able to connect to its network. (I imagine that that's the same way my old Lexmark printer that
did function through my AE worked.)