All Yaris versions have handbrake, so of course the GR Yaris has it. Corolla and Yaris Cross on the other hand have e-brake. So it is not a definite thing yet. Anyway, it is ok if they bring a manual Supra, but it would not be my choice, and of many other people either. The Supra does not have the success it deserves, but it is not surprising, there is more to cars than just engineering, there are also very many irrational reasons.If the GR Yaris had it, then the GR Corolla will have it as well.
The reason being that the GR Corolla will be using the GR Yaris' GR-Four system. One very cool thing that the GR Yaris can do is that when you pull the handbrake, it disconnects the transfer case for the AWD system and one can do hellacious turns and drifts, rally style.
Having an electronic handbrake would deny users of that feature in the car.