I think this must happen all the time. As they say, ideas are cheap. It's likely that ALL of them had the seq-to-seq idea cross their mind at some point before

I think this must happen all the time. As they say, ideas are cheap. It's likely that ALL of them had the seq-to-seq idea cross their mind at some point before it was acted on, so if credit is assigned to whoever said it out loud first, there's going to be disagreement, since most people don't remember the full details of every conversation. It's also possible for someone to be skeptical of their own idea, so that argument isn't compelling to me either. Ultimately credit usually goes to the people who do the hard work to prove out the idea, so it seems like the system worked as intended in this case.