
Quoting
Mr. Knowitall
It has been done, but very short visits run the risk of being determined not to constitute "residency". That's also a slow way to fulfill the HRR, requires careful documentation and record-keeping, and creates some potential for confusion or disagreement when you later apply for another visa, and thus is far from the simplest way to meet the requirement.
That is just plain wrong. A F1 visa is a non-immigrant visa, and is thus available to a person who previously held a J1 visa even if they have not yet fulfilled the HRR.