The pinch test is particularly good at high throttle settings, but most engines are not responsive to a pinch test at idle.

I've seen properly tuned engines continue to run for 15 seconds and more with the fuel line pinched, where-as at high throttle the results are immediate.

The rather low and slow fuel flow at idle masks the result of a pinch test.

The ignitor removal lets you quickly focus on an approximate setting. Then you can use a pinch test to verify the results. Fully pinched off the engine should run, and then after a while briefly speed up and finally stop once tuned.