no 1/2 circles do not go into corners, then then would not be 1/2 circles
OP if this is intro or training level test then I would not expect a green horse to go deeply to corners before and after the CL unless you can show it with exceptional skill.
You should not be penalized by riding the turns onto and from the CL as a half circle, but you may earn a slight bonus for a deeper corner, if done correctly and well.
I dont recall ever seeing a USEF test with such a directive, though will admit to not really paying attention. The turn onto/off the CL should be something your trainer should be schooling with you as part of ring craft for showing
without seeing your actual test I cannot imagine what the judge saw. You may have over shot the orientation of the straightness on the long side ; not straight on the long side at the letter.
Sometimes it helps to read your comments with the unsaid words " for better score" before or after the comment