The 2090, 2490, and PA231W are all standard gamut monitors so the gamut of those 3 are going to differ significantly from the P221W, PA241W, PA271W, PA301W, and LCD3090W.
That's another reason why I think they may be using a firmware based solution. If firmware is at play then they could have a correction matrix for an average of the standard gamut monitors, and an average of the wide gamut monitors. Using filters would however require at least two different models of the puck.
Cheers, Joe