Where is this behavior specified?

[EugeneNeuron]

In README you say that this is a specified behavior that temporary buffers do not inherit the calling buffer's environment. Maybe you can remember where it is specified?
I didn't find it in info (elisp) Current Buffer.

[purcell]

I meant this in the sense that with-temp-buffer does nothing to propagate the calling buffer's environment to the new temp buffer, and the fact that process-environment is set as a buffer-local in the calling buffer does not automatically cause the variable to be set buffer-locally in the new buffer.

[EugeneNeuron]

Thank you, @purcell