Hoo, boy, dummy learns to sew.
So apparently, you need to pay attention to the direction that you sew in, or "directional sewing." I... did not realize this was a thing.
"On an A-line skirt, for example, stitching the front and backs together from the hem to the waist on one side seam and from the waist to the hem on the other side seam renders one side longer than the other."
I am positive I've done this.
Edited to remove facepalm gif, cuz it quickly got annoying.
Imagine facepalm gif here.