NEC's S-PVA P221W, IPS 2090/2190/2490/3090 and p-IPS PA231W/PA241W/PA271W all have the same viewing angles spec of 178 degrees. IPS and p-IPS are supposed to have superior viewing angles as compared to PVA so what is going on here?

I know there are other differences between these monitors in terms of bit-depth, resolution, color gamut coverage, response time, etc., but I am really at a loss about the viewing angles.

Any insights are really welcome!