Cudnn cudnnConvolutionBiasActivationForward question and suggest

cudnnConvolutionBiasActivationForward not support x point to the same buffer as z or y
I understand x != y, but why x can not be same with z (z and x are both read only)? Some skip layer may be this case.
https://docs.nvidia.com/deeplearning/cudnn/api/index.html#cudnnConvolutionBiasActivationForward

@AakankshaS