There was something about that a long time ago in one of the updates.
IIRC it was about a fix to make circles come out like circles and not stepped trapezoids, and squares to have actual squared corners. Something like that.
I'll try to find it. But hey, at least you can change it back. They made a whole update just for you because you fiddled with a setting
EDIT: Found it. It's for engraving, not printing. For making geometric shapes to look like, well geometric shapes... Here's the early thread on it, where it was buried in expert settings before it was moved to machine settings in FS 0.6.2 http://forum.flux3dp.com/t/unhappy-with-svg-engraving/2341