Is doing a transmission reflash the same as the relearn procedure?
Not necessarily, A reflash may include new programing. Relearning is something your car does automatically after the power is disconnected from the computer.
Some newer, fancier cars may nor relearn everything when it comes to the radio or anti-theft systems.
A reflash is installing the most up to date program for your transmission. The technician would have to down load the program from Subaru and flash your TCM. Since your transmission is probably well broken in if not well worn, the program will still have to relearn shift parameters that let your transmission shift optimally.
A relearn is the adaptation that a transmission program does to match shift parameters to the state of your transmission clutches and your style of driving. If you have a max effort style of driving, it will adapt the shift patterns to give a crisp, no slip, harsh engagement. If you have a more laid back driving style, it will adapt the shifts to a bump free engagement i.e. softening up the shift.
Hope this helps.