I always thought so, but I've read and heard different answers about it. A plebe may have been a standout football and baseball player at HS, but not be recruited for those sports. Then he comes to plebe summer and and blows everybody away in a sprinting event. Now the track coach wants him on the team. Does he need to then be registered? The coach and athletic dept would know. What about a kid who wrestled at the d3 level for 2 years? D3 does not require NCAA clearinghouse registration. On the NCAA website, it says that a d3 student transferring into a d1 or d2 program needs to look at that school's eligibility requirements. It does not say that a transfer student from a d3 school needs to be registered. There are so many grey areas. My son is registered anyway, because he needed to be for the official visits he too at the civilian schools.
I'm sure this is why every D1 athletic program has a compliance specialist. In the end, if you have any desire or chance to be an athlete at the D1 or D2 level, get registered and have all your bases covered.
To be clear, I agree with you all. But the original question was does the athlete need to be registered out of High School. I am sure there are many plebes who were not registered out of HS that ended up being varsity athletes at a SA. And I'm sure the compliance depts made sure they were registered if they needed to be.