From a usability stand point the sport shifter never moves its always in the same spot regardless of which sweeping turn your going through so compared to the lame paddle shifters that spin around the steering wheel its a much better set up for those of us who might want to go from 2nd to 3rd in anything other than a strait piece of road.I do really missed the floor sport shifter instead paddle shifter. I felt it little more fun that way. Paddle shifter is kind of useless but I use them for up or down hill.
My 2006 Legacy sedan has sport shifter and it was easy to use. I cannot remember if my 2000 Legacy GT sedan has the sport shifter. It was long time ago.
The way I drive, I rarely use both hands on the wheel. I only use both hand while turn the wheel. Just bad habit.
2000 Legacy had the lazy 4eat AT in it with no sport shift - sport shift arrived in 2005 if I recall.
And yes your correct bad habits regarding hands on the wheel and correctly thumbs out not in - on a AWD car is actually an even bigger deal than say the old beater RWD buick.
Given you have power to the front wheels which can easily hook into rough pavement and spin a wheel right out of your hand - or break a thumb hooked inside the wheel.