[black_beauty]

or is setting the wheels wider mostly for the look?
a little math, below
front spacer sizes (mm) 10,12,13 increase track width 1.3-1.7%
rear spacers 12,13,15 inc by 1.5-1.9%
Different spacer combinations affect the front/rear width ratio, while, obviously, the wheelbase stays constant.

Would a car engineer, or anyone who could appreciate what those differences might mean in terms of driving, and say, of course it would change the driving feel, or are those negligible changes and adding spacers, without lowering the suspension, would be mostly for the look? Certainly, there's a ton of reasons to get the look you want, so go for it!
The bonus could be both, wider feel that translates well behind the wheel, and the wider look.
Or maybe the engineer is saying, why are you messing with the design?
......

spacer pair (mm) | track (inch) | track with spacers | Percent increase | track/wheel base | track/wheel base with spacers | increase (inch) | increase (mm) |

front | 10 | 60.5 61.29 1.30 0.547 0.554 0.787 20
front | 12 | 60.5 61.44 1.56 0.547 0.556 0.945 24
front | 13 | 60.5 61.52 1.69 0.547 0.556 1.024 26

back | 12 | 62.1 63.04 1.52 0.561 0.570 0.945 24
back | 13 | 62.1 63.12 1.65 0.561 0.571 1.024 26
back | 15 | 62.1 63.28 1.90 0.561 0.572 1.181 30

wheel base (inches) 110.6

front/back stock = 0.974

front/back with spacers | front spacers | rear spacers
0.972 10 | 12
0.971 10 | 13
0.968 10 | 15
0.975 12 | 12
0.973 12 | 13
0.971 12 | 15
0.976 13 | 12
0.975 13 | 13
0.972 13 | 15

[VMRWheels]

Based on my personal experience, I have never noticed a difference with spacers added.

[black_beauty]

Thanks, that's what I expected.