So, apparently NieR Replicant was a Japan-only release, which has recently been "updated" and released globally with the official title NieR Replicant™ ver.1.22474487139....
After doing research between the four various titles - NieR, NieR: Replicant, NieR: Gestalt, NieR Replicant ver.1.22 - as well as additional information provided by Vemonus, nier-replicant-1.22474487139 needs to be a separate tag to differentiate it from the standard nier
The 1.22474487139 version of Replicant contains exclusive content including a new story segment as well as a fifth ending
I believe it's safe to keep the base tag nier, and create the following synonyms:
My researched concluded there are not enough (if any all) functionality or mechanical differences to warrant having separate tags for the various versions.
In Japan, NieR:Replicant and NieR:Gestalt were the same game with different titles for PS3 and X360 respectively. The only major difference was the main character's age and role to a secondary character. There were some minor differences as well, but nothing to suggest separating these tags.
Outside of Japan, the version titled NieR was simply the NieR:Gestalt version.
The globalized version of NieR:Replicant ver1.22474487139 is an HD Remaster of the Japan only version of NieR:Replicant, and my researched conducted only graphics and framerate are the only major differences.
Recording what I'm about to do for posterity, based on the comments, answer, and linked question.
Update nier description to clarify it's for all permutations of the original game, with nier-replicant and nier-gestalt requested as synonyms. Keep nier-replicant-1.22474487139 as a separate tag to be used with it when the question is about the updated version, and nier-replicant-1.22 as a synonym.
As far as I can see, there are no users with sufficient rep to make synonyms on these tags yet, so that will have to wait. Fortunately it's not much of a burden to do manually.