That just creates the same questions for why this region of space is so dominated by 'matter' while adding a new one that another vast region of space is dominated by 'anti-matter'.
If you can come up with some compelling mechanism for it then sure it may be possible, but currently that seems to be more complex and fails to provide any support of any kind.
It's pure speculation, but I am suggesting that instead of some sort of annihilation imbalance, the mechanism might be a sorting process that causes antimatter and matter to collect into horizon-shaped pockets.
If there were such a sorting process that was inherently linked to cosmological horizons, it could explain both where the antimatter went, and why we don't see an annihilation zone where the boundaries meet.
The problem is your sorting process is identical to your original statement. It's like saying "why is the sky blue" > "air is blue". You need to make predictions that are different from your observations.
On the other hand if you say something like "Air becomes blue when it's colder." Then you can actually test what's going on and falsify the statement which may lead to progress.
Suppose you suggest the output of this experiment will change over time. Now, waiting a billion years is not going to happen but adding even more digits of accuracy may be possible.
If you can come up with some compelling mechanism for it then sure it may be possible, but currently that seems to be more complex and fails to provide any support of any kind.