Not to sound patronizing, and I COULD be wrong, but I believe this is sort of basic knowledge: anything you do to treat hair loss takes weeks, if not months, to result in any kind of difference, good or bad. So in other words, you won't shed the next day after using SA, or any other product.
My guess is 1) the minoxidil is the cause for the shed, and 2) you might notice the sudden, large number of shed hairs because minoxidil synchronizes your hair's growth cycles. But do some homework on this site before you take my word for it.
I never knew that SA helped the scalp absorb minoxidil better. I'll have to research that one more myself. I want to agree simply because I heard that SA makes rosacea (redness of face) worse with some poeple. I think this happens because it dialates the capillaries. Not sure.