I should have been more clear about my statement that you quoted.
Road tires' calibration constants are probably less sensitive to temperature change than bigger tires, like mountain bike tires. My experiments show this, as the Gatorskin tires were less sensitive to temperature than both the Primo and Bontrager tires. But it's not because they are narrower or because of the higher initial pressure. It's because of other reasons.
The comparison between the 23mm and 32mm Gatorskin tires shows that tire width on its own doesn't matter. Those two tires had nearly the same cal constant sensitivity to temperature change.
The tests for all the tires with two different initial pressures shows that pumping your tire up to its maximum pressure isn't going to make it less sensitive to temperature change.
So yes, you should use a road bike tire to measure courses. But don't worry if it's 23mm, or 28mm, or even 32mm. And don't worry about pumping it up to its maximum pressure every time before you measure.