As far as I know, Ugurcan is not responsible for integrating the content into the game. We can ask him but I don't know his username in here. But the issue is not that implementation, the issue is the current implementation we have. It's causing performance problems.
So I'm not entirely sure who's adding those sounds and based on how but the current implementation is pretty straightforward which is causing issues performance and ambience-wise. I'm pretty sure if Game Designers come to Ugurcan and say "Hey look, we need battle sounds based on unit count and unit type" he wouldn't be super happy but he would do it in no time. Once he is ready with the content person who's responsible for adding it can add it into the game with the logic I explained above. This, essentially, should work, since with that ambience sound, all that matters is distance and unit cluster count which can be checked easily ( since AI is already doing that ) and the sound itself will be 2D on the game level. Would that sound better? I think yes but the only way to find that out is by trying and listening. Perhaps they tried that already, I don't know - we can only ask them but I seriously have no idea who's working on that and can answer this question in the forum.
But I think they are already cutting off the sound after a certain radius since we are not hearing the enemy army marching toward us unless they are super close. So my guess would be that they have some way of "improving" performance if the entity is very far away. But that's not enough and it's also killing the overall battle feeling because there is no "replacement" for that reduction, not even a fake one.
Yes that implementation would improve the performance by taking the load off from CPU.