The binaries are shipping with cudatoolkit=9.2 or 10.1.
If you specify 10.2, you might get the package from another source and PyTorch might fall back to an older release.
I just tested this command and got the following suggestion:
## Package Plan ##

  environment location: /home/pbialecki/anaconda3/envs/tmp

  added / updated specs:
    - cudatoolkit=10.2
    - pytorch
    - torchvision


The following packages will be downloaded:

    package                    |            build
    ---------------------------|-----------------
    cudatoolkit-10.2.89        |       hfd86e86_0       364.5 MB
    pytorch-1.0.0              |py3.7_cuda9.0.176_cudnn7.4.1_1       498.7 MB  pytorch
    torchvision-0.2.2          |             py_3          44 KB  pytorch
    ------------------------------------------------------------
                                           Total:       863.2 MB

The following NEW packages will be INSTALLED:

  ninja              pkgs/main/linux-64::ninja-1.9.0-py37hfd86e86_0
  pytorch            pytorch/linux-64::pytorch-1.0.0-py3.7_cuda9.0.176_cudnn7.4.1_1
  torchvision        pytorch/noarch::torchvision-0.2.2-py_3

As you can see, PyTorch would be downgraded to 1.0.0 with CUDA9.0.