My goal is to build bows that are balanced at full draw... meaning, at full draw the way I hold the handle and string, both limbs will exert equal strain on the string, resulting in a bow that doesn't try to tip in the hand during the draw, with the nock traveling straight back perpendicular to the handle, and straight forward upon release, with both limb tips arriving at true brace simultaneously. If one limb's strength (relative to all factors) is stronger, the nock will be pulled toward it during the draw relative to the shelf, and move away from it upon release. I don't want the nock end of my arrow treated that way. As Del mentioned, the string will try to stop them both at the same time, but a stronger faster limb gets there first, while the weaker acting limb is still on its way. This 'distorted brace' happens for an instant until the bow can 'right itself'. This is probably the instant we see in your pictures above.
If one limb is stronger than the other, and we work to balance them, it doesn't matter if one is weakened or the other strengthened, but usually it's easier to remove wood from the stronger.
If you're building symmetrical bows, tillered positive, with the shelf 2" above the center, you have probably become used to the feel of them shifting from static balance(at brace) to dynamic (at full draw) and posible putting extra pressure here or there where you feel it's needed. A bow that is balanced might feel odd to you and you may need to make some adjustments.
You said you dont know how someone could shoot a bow with a stronger top limb. First understand that just because a bow shows the top limb stronger at brace doesn't necessarily mean it will feel and ACT stronger at full draw... or any time during the draw. Much depends on design and the shooter's peculiars.
I make my bows to feel balanced at full draw, and depending on those things mentioned, and others, sometimes my bows are tillered negative, sometimes even, and less often, positive... but they ALL feel balanced the same at full draw.
