Differential Pair Width and Seperation

[navig2712]

Just out of curiosity i was looking into ESP32 based boards such as EVA,GATEWAY,POE,POE-ISO and found the differential pair used for Ethernet is all different sizes(ie: width and space between them) even though the board thickness is 1.6mm for all.

so with an assumption that H(Height of dielectric between two layers) will be 0.48mm(normally) i tried calculating the Zdiff for these tracks which is surprisingly coming around 130ohm which is way way off from what it should be(100ohm).

Does any1 have any explanation why its done this way??