The different suspension of the WRC27 I would assume. The Hyundai camp told that they expect the 27 to be much better in this regard. All this is just bandaids to somehow get out of an imposible...
1 Solberg 2 Ogier 3 Neuville 4 Evans 5 Fourmaux 6 Pajari 7 Sordo 8 Armstrong Vincemon1285
1 Fourmaux 2 Solberg 3 Sordo 4 Ogier 5 Katsuta 6 Neuville 7 Sesks 8 Mikkelsen Maui J.
1 Ogier 2 Neuville 3 Fourmaux 4 Evans 5 Sordo 6 Katsuta 7 Armstrong 8 Sesks EdReis
Hyundai will not develop the Rally2 kit (at first, but let's be honest here, never) https://dirtfish.com/rally/wrc/hyundai-isnt-planning-a-rally2-kit/ That leaves us with Toyota and M-Sport...
WRC mainclass from 2027