Seeing as no one else has jumped in to respond I'll give it a try.
I'm reasonably confident that "biostance alignment" is the same as what most of us just refer to as alignment. Some use the word "balancing" or "boot balancing".Whatever you call it, it involves adjusting equipment to match your unique body. Achieving proper alignment results in optimized performance from you and your equipment.
Adjustments may be made to the zepa, (the plastic piece in the boot under the liner) insoles/custom footbeds, boot cuff, boot sole, and binding position. The insoles, or footbeds, provide for both comfort and proper position of the ankle bones. Some tweaking of heel and toe heigth can be done with the zepa and footbed.(this is called adjusting ramp angle)The boot sole can be modified by adding shims under the toe or planeing to achieve both for/aft and lateral alignment. Lateral adjustment is called "canting". Fore and aft adjustments can be done by either changing boot toe and heel height, or by raising or lowering the height of the binding toe or heel. Height adjustments to binding or the outside of the boot change whats called "delta".
Moving bindings forward or back (Campbell balancing) is maybe the last step. For some people, the ski manufacturers chosen position for the bindings may need adjustment.
Does going through this process make a difference? If you were blessed with perfect genes to make a skier, probably not. If you are like about 90% of the population, it helps. How much it helps depends on how far out of alignment you are, what your skill level is, and how serious you are about performance.
I've watched people with serious alignment issues and minimal skills have a whole lot of fun skiing. For me, every time I've tweaked my alignment, skiing got easier, took less energy, and balance and skills improved. Some people deny that any of this is needed except when there are extreme anatomical issues. I've always suspected that they were part of that blessed 10% that got all the good genes.