It is Volta, but it is not the PCIe version (not dGPU)…the GPU is directly integrated with the memory controller on embedded versions (an iGPU). If you were to compile CUDA software, then Xavier and Xavier NX would use:
(which is Volta)
If you compile CUDA software with 72, and this complains, then it would be a problem to investigate.
NOTE: There are some GPU discovery applications, e.g., nvidia-smi, which rely on PCI. Those will be missing and fail to identify the GPU on any Jetson.