Welcome to the forum.
It won't be Toyota based underneath, instead it will ride on a platform from BYD. Toyota is usually good at bringing cars from partnership up to their standard but I think some folks might still be concerned. Are you?
Due to the problems with the Bz4x yes, I'm very concerned. This sedan seems to be only for China, Chinese quality standards are often not up to Japanese standards. The Bz4x had a false start, hope Toyota has learned from this.
And I really do not understand why Toyota, nr 1 carmanufacturer, depends on Byd for their BZ lineup..... . Only reason can be tgey have, and stil are, neglect the Bev transition. Kia Hyundai are far agead of Toyota. And Toyota still not get it. The lack of focus on Bev development has damaged the reputation of Toyota beyond repair. In Europe the Bev is hot and already good gor 16% marketshare, Norway will ban the petrol car in two years, a big market for Toyota until recently. Toyota has no Bev available in Norway and sales are very very poor now. The bev teansition goes to slow, it will cost Toyota marketshare and already reputation damage. Maybe their solid state battery will cone to the resque, but I doubt. Think Volkswagen will have the solid state premiere instead, tge have far better narketing and product strategy. For me, Toyoda has to resign immediately, he has made costly mistakes.