Should double glazing sit evenly in brick to brick window space?
Probably a case where the window can look good from the outside, or the inside but not both due to the way the house was constructed.

They chose to not make it look like an eyesore from the outside where everyone walking by would notice it.

It's one of the irritating factors of retrofitting something into something that was never built to those dimensions. You would need to hire a finish carpenter to widen the interior opening to give it that aesthetic balance as long as brickwork would allow it.