People are missing Jeff's point that "the profile software will be expecting the patches to be within a normal range".
If you alter exposure of the chart you're going to alter the RGB values of the patches. If you ETTR by a stop or stop and a half you may throw the RGB values of the patches outside of the range that the profile creation software is expecting.
Example, I shoot a CC Passport at +1.5 Exp Comp and the light blue patch, top row, third from the left reads 83%, 84%, 94% in LR. Shooting the Passport at 0 Exp Comp the same patch reads 54%, 55%, 70%. That's a big difference and may be outside of the range of what the Passport software is expecting in reading the values captured by the camera to create the profile.