This is a high school student he is writing for, one that he presumably has only known for a very short time – 4 months if she started the college courses in September. He has most likely had her for one class. He is going to need a lot of input – where we disagree is what form of input is acceptable.
I pulled up my son’s “brag sheet” that he did early last Fall. If you added an intro and conclusion along with some definitive articles and pronouns it would not be a bad letter. I am pretty sure that his counselor and teachers did not use his brag sheet as anything more than supplementing what they already had to say abut him. Perhaps some cherry picking of accomplishments that might apply to their particular discipline and then adding athletics or leadership positions as a general endorsement. Why is it so hard to believe the professor in the OP would do the same thing?
I also think most college professors are very aware of these sorts of issues and would tread carefully.