Shape of circle annotation without appearance stream isn't round
See #988 (closed) for renderings... the shape looks kindof weird.
I wonder if it is the Bézier contant? Poppler uses 0.55228475 in poppler/Annot.cc; https://spencermortensen.com/articles/bezier-circle/ recommends 0.551915024494; Apache PDFBox uses 0.55555417 which was calculated from sampling content streams generated using Adobe Reader.