Not much to elaborate. You're told to bring a stack of documents if you have a scientific or technical background, such as CV, a list of publications, an invitation letter from your US host, a letter from your university etc. If the embassy official isn't satisfied, you are asked to send more documents to a state.gov email address. On one occasion they wanted more information about my work as a programmer before I started my PhD. When they asked me for more documents I was tempted to joke that it doesn't matter what address I use, the email will reach the required destination anyway.

It sounds like they're doing more than simply determining ones suitability for entry.

> It sounds like they're doing more than simply determining ones suitability for entry.

Did you honestly think that's all they are doing?

They can do anything they want, for as long as they want.