4 lines, 8 spots where line changes to curve and 4 curves
If you have to process the fact that a line changes into a curve, then why don't you have to process that two lines are intersecting, or 'changing' at a 90deg angle?
I thought about that and mathematically it makes sense, but that's just not how I experience it. The corner is "simple" there is nothing there for me to process, so I don't need to notice it.