I don't put symmetry first on my priority list of carving 'do's and don'ts'.
Contemporary building:
A rifle is a work of art; and there are limitless approaches. There are few rights and wrongs.
You can be loose with your application of design, shape, carve and engrave what looks right, feels right to you. Conversely, you can be tight and exacting with your design work.
The most important thing to me is that I have to be happy working on the gun. If I am doing something that sticks in my craw, it takes all the fun out of it. I am working for me, not anyone else.
It comes down to what you enjoy, how you like to work, what you envision your finished piece to be. You have to do a bit of soul searching to figure out how each gun you build is going to look like in your mind, get your concept clear before you begin. A drawing helps tremendously in this, not only get your stock shape down, but WHERE the components go, how they relate to each other, where the lockbolts must pass, where the rr channel lies in relation to the lock and barrel, and on and on.
Some of my guns have been tight and exacting, and some very loose, designed on the fly. I have to say that I like the 'design as you go school' because my concept changes as I build, sometimes radically. The downside to this is that I sometimes work myself into a corner.
But un-symmetrical scrolls on either side of the wrist won't give me any problems. I understand that completely. The gun would look better if you use more of that wide open space between the patchbox and scroll.
But it's all opinion, and there's plenty of that here, so in the end, you read all the opinions, and do it the way you're gonna do it anyway.