Actually you are correct that a B1 visa is all you need. Observations and attending omeone-time seminars (i.e. not recurring ones) qualifies as business, and not study.
However, in this case, what is correct by definition doesn't matter, because the consulate issues the visa; as such you have to go by their instructions.
So, if you want to get into the US, you have to apply for a J1 visa