This is caused by an optimization where things are converted to polyline so as to draw more quickly.
If you view in 3D using a current version:
Please try the nifty new beta:
Or in a 3rd party G-code viewer:
or actually cut things you will see that they are a bit smoother than that, and if you check the G-code:
X50.964Y30.178
X51.098Y30.398
you will see that the line segments which are actually cut are very short:
compared to the ones used for the Toolpath pane preview:
