It depends on the material condition for the feature and where it sits in the order of precedence of a referring callout as to what needs to be done to simulate it.
In many cases it isn't required to find the exactly perfect high points, only to be certain that the finding is within the bounds of accuracy required to be sure the check is a good one.
For example, on a simple (as anything can be simple) length measurement: If the tolerance is +/-1.00 unit and the accuracy is only .25 units on the measuring equipment, but the measure is .25 from nominal, then it is likely the part is acceptable and lies somewhere between 0.00 and .50 of nominal. If a different copy of the part is at .999 and the measure with the .25 accuracy is .99, then one can't be sure, so a more accurate method is required for that copy.
The theoretical gauge is perfect, but practical applications are always a trade-off between cost, time, and likelihood of accuracy.