Its OAuth documentation - its a very well described standard protocol. Most of the OAuth documentation looks and reads exactly like this. The only "smoking gun" is the "random" value used for the state parameter, which seems to be copied over - and developers copy other products/sites documentation ALL THE TIME.

While there is substance in the post that some other company is building the same product, saying that its literally cloning it and using documentation similarity for a standardized protocol is not really cutting it.