A student asking if a company is hiring full-time engineers is not naive in the slightest. You're writing purely from the perspective that all companies behave exactly like Twilio. In my experience (granted this was a couple of years ago), many companies at career fairs are sometimes looking only for interns. Some are just there for some advertisement, not hiring but still maintaining a relationship with the company.
With regards to the point about Java, rather than looking at just the language, I would think it's more worthwhile to see what a person has built with the tools they have knowledge of, rather than extrapolating that they are unwilling to learn something new.
With regards to the point about Java, rather than looking at just the language, I would think it's more worthwhile to see what a person has built with the tools they have knowledge of, rather than extrapolating that they are unwilling to learn something new.