That's what the developers named the content tiers this expansion. 4.0 was Deltascape, 4.2 was Sigmascape, and 4.4 is Alphascape. Raiders realized that was stupid and would be confusing to newer players who wouldn't understand the progression.Whiskey Tango Foxtrot is all this alpha, sigma, omega scape version 1,2,3,4,5 ect? Are they different version of raids?
Since Omega is the big bad of the story and it's all "Omegascape" players named it O1S through O12S instead of having D1S-D4S, S1S-S4S, A1S-A4S. FF14 has two difficulty versions, Normal and Savage which is where the "S" comes from.