I personally suspect that the true reason for that integrated GPU is the USB4 support. Always having that integrated GPU allows for full USB4 directly on the motherboard without needing hacks like looping a DisplayPort cable from the discrete GPU to the motherboard. And I believe it's possible to render in one GPU but present the output through another GPU, so you could in theory even use a discrete GPU for rendering while the output is going through the USB4 socket on the motherboard, without any extra cables between the graphics card and the motherboard.