Isn't this how all of the "Sign in with X" work? It's the same with facebook and google also where you go through the same OAuth flow where it asks if you want to give this third party access to your data.
My experience is that when I sign up to a service with a previous account, the previous account tells me what data the new service will have access to, and then the new service has a couple of more steps to fully create a new account.
In this example it was "Log in with LinkedIn" -> immediately to the front page. I've never had that before.
In this example it was "Log in with LinkedIn" -> immediately to the front page. I've never had that before.