That would mean no need to make a GR4 version just some basic 3-door cars so why have they bothered ?
The GR4 is much different to any other Yaris, its not just the number of doors. It has a lower coupe-style roofline and the wider body and arches. Toyota TGR wanted this for the WRC car for better aero, a wider track and better placement of the rear wing.
https://www.roadandtrack.com/new-car...ation-special/
"This is a stunning machine and a true homologation special, for while it's unique four-wheel-drive system isn't eligible for WRC competition, the specialised, low-roof, lightweight three-door bodyshell most certainly is. To qualify to use the new car in the WRC, however, the company will have to build 25,000 road-going models in a single year."
https://www.telegraph.co.uk/cars/new...road-unveiled/