Usually between one's junior and Senior year Cadets attend Leader Development and Assessment Course which used to be called ROTC Advanced Camp.
Source. I also just contacted a battle buddy who just finished an assignment as a Professor of Military Science and he concurred with position.
They only exception is if someone is enrolling in a two year college, like North Georgia, and this is the underwhelming minority of Cadets.
Thanks for your efforts and recent ROTC info validation from a serving officer. My experience was in the 70s yet I found that it was still very similar today, just as you describe. I’d also had interaction with the current cadre at my alma mater as part of an alumni weekend. MG01 has a very fixed position that was not moved by my link.
It might be the wrong term to use (e.g., “enlistment”) for last two years, but you do sign papers committing you to the program and you are obligated to a specified number of years on active duty when a particular service springs 100% for your room, board, books, and tuition. READ fully the contract you are signing because there are certain defined recourses (both parties) for not fulfilling the terms of the contract.
I don't worry about this stuff any more because I did my 24 years and I'm now retired.