The APIs in the blog post were not invented by Smartcar. Like most HTTP-based APIs, Smartcar's authorization endpoints follow the OAuth 2.0 standard, which specifies the exact parameter names and how they should work: https://tools.ietf.org/html/rfc6749#section-4.2.1
Maybe Otonomo copied more than that, but the blog post only covers the OAuth stuff, so it's incorrect to conclude that Otonomo "stole the whole public facing architecture".
Yea, Otonomo obviously lifted from Smartcar's docs, which is lazy and unclassy, but it's not _that_ big of a deal. I bet most people who implement OAuth end up using an existing company's API docs as a guide; they just usually know better than to copy entire sentences.
The Smartcar blog post is over the top. It makes it seem like their OAuth docs are their value proposition. I really hope it didn't take "months of ideation, engineering, chatting with customers, and iteration" to dream them up.