So it's not as simple as one part being a standalone bleach, and the other being standalone fixer. B is a standalone fixer, but A depends on B to work?
Part A converts Silver to Silver ions, and Part B forms a soluble complex with Silver Ions. If you leave out Part B, you need an anion to make the Silver ions happy, preferably one the Silver ions really like, e.g. Bromide.
I have seen a report where someone just tried to mix Part A and Part B into separate bathes and he got brown stain on his slides - an indication that Silver was left behind.
Trying to be the best of whatever I am, even if what I am is no good.