No, Archbang is not Arch Linux. The Archbang developers have consistently made decisions that mean Archbang differs from Arch.
Initially it was around things that could be considered "convenience"1, like installing from the AUR by default, by default including files in
/etc/sudoers.d/ or having a keybind for
Over time, and particularly with Arch's recent move to systemd, the differences have become much more marked; to the point where now the Archbang developer is musing about using a Slackware base.
If you want to install Arch, install Arch; but don't be misled into thinking that by installing Archbang you are going to be running Arch Linux.
1. Note, none of these things is, from an Arch point of view, either convenient or a particularly good idea, and the last of the three can only be described as reckless.